The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A210478

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A210478

Meandric numbers for a river crossing up to 17 parallel roads at n points.
(history; published version)

#16 by T. D. Noe at Tue May 08 00:01:17 EDT 2012

STATUS

proposed

approved

#15 by Robert Price at Mon May 07 20:27:30 EDT 2012

STATUS

editing

proposed

#14 by Robert Price at Mon May 07 20:27:27 EDT 2012

CROSSREFS

Cf. A204352, A208062, A208126, A208452, A208453, A209383, A209621, A209622, A209626, A209656, A209657, A209660, A209707, A210344, A210478, A210567, A210592 (sequences for 3 to 19 parallel roads).

STATUS

proposed

editing

#13 by Robert Price at Mon May 07 20:12:23 EDT 2012

STATUS

editing

proposed

#12 by Robert Price at Mon May 07 20:12:12 EDT 2012

NAME

allocated Meandric numbers for Robert Pricea river crossing up to 17 parallel roads at n points.

DATA

1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28178, 76539, 240370, 665129, 2123439, 5964691, 19302315, 54898415, 179696520

OFFSET

0,3

COMMENTS

Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 17 parallel East-West roads n times.

Sequence derived from list of solutions described in A206432.

CROSSREFS

Cf. A005316 (sequence for one road; extensive references and links).

Cf. A076876 (sequence for two parallel roads).

Cf. A206432 (sequence for unlimited number of parallel roads).

Cf. A076875, A076906, A076907.

KEYWORD

allocated

nonn,more

AUTHOR

Robert Price, May 07 2012

STATUS

approved

editing

#11 by Robert Price at Mon May 07 20:12:12 EDT 2012

NAME

allocated for Robert Price

KEYWORD

recycled

allocated

#10 by T. D. Noe at Mon Apr 16 12:16:32 EDT 2012

STATUS

proposed

approved

#9 by Joerg Arndt at Fri Apr 13 08:01:03 EDT 2012

STATUS

editing

proposed

#8 by Joerg Arndt at Fri Apr 13 08:00:59 EDT 2012

NAME

Least significant base 10 digit of doubled Fibonacci numbers.

DATA

2, 2, 4, 6, 0, 6, 6, 2, 8, 0, 8, 8, 6, 4, 0, 4, 4, 8, 2, 0, 2, 2, 4, 6, 0, 6, 6, 2, 8, 0, 8, 8, 6, 4, 0, 4, 4, 8, 2, 0, 2, 2, 4, 6, 0, 6, 6, 2, 8, 0, 8, 8, 6, 4, 0, 4, 4, 8, 2, 0, 2, 2, 4, 6, 0, 6, 6

OFFSET

1,1

COMMENTS

These numbers are first digit (mod(10)) of doubled Fibonacci numbers. They have cycle period of 20 of them.

FORMULA

2F(n) mod 10, where F(n) is the n-th Fibonacci number

EXAMPLE

a(11) = 8 because the 11th Fibonacci number is 89, and twice that is 178, which leaves a remainder of 8 when divided by 10.

MATHEMATICA

Table[Mod[2Fibonacci[n], 10], {n, 100}] (* Alonso del Arte, Mar 21 2012 *)

CROSSREFS

Cf. A000045 (Fibonacci numbers), A055389 (doubled Fibonacci numbers), A003893 (Fibonacci numbers mod 10). A000213, A000288, A000383, A166516, A166536, A006355

KEYWORD

nonn,base

recycled

AUTHOR

Lee SeungHyun (thomas0210(AT)naver.com), Mar 21 2012

#7 by Alonso del Arte at Wed Mar 21 22:10:04 EDT 2012

CROSSREFS

Cf. A000045, (Fibonacci numbers), A055389 (doubled Fibonacci numbers), A003893 (Fibonacci numbers mod 10). A000213, A000288, A000383, A166516, A166536, A006355, A055389

Discussion

Wed Mar 21