The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A220347

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A220347

Permutation of natural numbers: a(1) = 1, a(triangular(n)) = (2*a(n))-1, a(nontriangular(n)) = 2*n, where triangular = A000217, nontriangular = A014132.
(history; published version)

#20 by Alois P. Heinz at Sun Dec 05 17:27:26 EST 2021

STATUS

proposed

approved

#19 by Jean-François Alcover at Sun Dec 05 11:27:09 EST 2021

STATUS

editing

proposed

#18 by Jean-François Alcover at Sun Dec 05 11:27:04 EST 2021

MATHEMATICA

a[n_] := a[n] = With[{r = (-1 + Sqrt[8n + 1])/2}, Which[n <= 1, n, IntegerQ[r], 2 a[Floor[Sqrt[2n] + 1/2]] - 1, True, 2 a[n - Floor[r]]]];

Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Dec 05 2021 *)

STATUS

approved

editing

#17 by OEIS Server at Fri May 22 05:28:37 EDT 2015

LINKS

Reinhard Zumkeller (first 250 terms) & Antti Karttunen, <a href="/A220347/b220347_1.txt">Table of n, a(n) for n = 1..10440</a>

#16 by N. J. A. Sloane at Fri May 22 05:28:37 EDT 2015

STATUS

proposed

approved

Discussion

Fri May 22

05:28

OEIS Server: Installed new b-file as b220347.txt.  Old b-file is now b220347_1.txt.

#15 by Antti Karttunen at Tue May 19 18:05:19 EDT 2015

STATUS

editing

proposed

#14 by Antti Karttunen at Mon May 18 15:20:58 EDT 2015

FORMULA

a(1) = 1; for n > 1: if A010054(n) = 1 [i.e., if n is triangular], then a(n) = (2*a(A002024(n)))-1, otherwise a(n) = 2*a(A083920(n)). - Antti Karttunen, May 18 2015

CROSSREFS

Cf. A000217, A002024, A010054, A014132, A083920, A220348.

#13 by Antti Karttunen at Mon May 18 15:17:19 EDT 2015

NAME

Inverse permutation of A183079, when seen as a flattened sequence. Permutation of natural numbers: a(1) = 1, a(triangular(n)) = (2*a(n))-1, a(nontriangular(n)) = 2*n, where triangular = A000217, nontriangular = A014132.

COMMENTS

Inverse permutation of A183079, when seen as a flattened sequence.

EXTENSIONS

Old name moved to comments by Antti Karttunen, May 18 2015

#12 by Antti Karttunen at Mon May 18 15:16:26 EDT 2015

NAME

#11 by Antti Karttunen at Mon May 18 14:58:43 EDT 2015

CROSSREFS

Cf. also a similar permutation A257797 from which this differs for the first time at n=15, where a(15) = 11, while A257797(15) = 9.