A046804 - OEIS

A046804

a(n) = p mod (p mod 10) where p = prime(n).

0, 0, 0, 0, 0, 1, 3, 1, 2, 2, 0, 2, 0, 1, 5, 2, 5, 0, 4, 0, 1, 7, 2, 8, 6, 0, 1, 2, 1, 2, 1, 0, 4, 4, 5, 0, 3, 1, 6, 2, 8, 0, 0, 1, 1, 1, 0, 1, 3, 4, 2, 5, 0, 0, 5, 2, 8, 0, 4, 0, 1, 2, 6, 0, 1, 2, 0, 1, 4, 7, 2, 8, 3, 1, 1, 2, 2, 5, 0, 4, 5, 0, 0, 1, 7, 2, 8, 2, 0, 1, 5, 2, 4, 0, 4, 2, 5, 0, 1, 0, 1, 4, 2, 2, 0

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OFFSET

1,7

COMMENTS

From Robert G. Wilson v, Feb 12 2014: (Start)

a(n)=0 iff p ends in 1 (A030430) or is a single-digit prime, i.e., 2, 3, 5 or 7 (n = 1, 2, 3 or 4),

a(n)=3 iff n is in A142087,

a(n)=6 iff n is in A142094,

a(n)=7 iff n is in A142330,

a(n)=8 iff n is in A142335.

a(n) can never be 9. (End)

REFERENCES

Idea derived from "The Creation of New Mathematics: An Application of the Lakatos Heuristic," pp. 292-298 of Philip J. Davis and Reuben Hersh, The Mathematical Experience, Houghton Mifflin Co, 1982. ISBN 0-395-32131-X.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Index entries for sequences related to final digits of numbers

EXAMPLE

prime(10) = 29, so a(10) = 29 mod 9 = 2.

MATHEMATICA

Mod[#, Last[IntegerDigits[#]]]&/@Prime[Range[110]] (* Harvey P. Dale, Jan 23 2013 *)

Mod[#, Mod[#, 10]]&/@Prime[Range[110]] (* Harvey P. Dale, Aug 22 2020 *)

CROSSREFS

Sequence in context: A324123 A016570 A070773 * A263211 A287571 A214316

Adjacent sequences: A046801 A046802 A046803 * A046805 A046806 A046807

KEYWORD

nonn,base,easy

AUTHOR

Enoch Haga

EXTENSIONS

Name edited by Jon E. Schoenfield, Jan 19 2023

STATUS

approved