A277097 - OEIS

A277097

a(n) = 5 - (prime(n) mod 10).

3, 2, 0, -2, 4, 2, -2, -4, 2, -4, 4, -2, 4, 2, -2, 2, -4, 4, -2, 4, 2, -4, 2, -4, -2, 4, 2, -2, -4, 2, -2, 4, -2, -4, -4, 4, -2, 2, -2, 2, -4, 4, 4, 2, -2, -4, 4, 2, -2, -4, 2, -4, 4, 4, -2, 2, -4, 4, -2, 4, 2, 2, -2, 4, 2, -2, 4, -2, -2, -4, 2

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OFFSET

1,1

COMMENTS

Except for a(1)=3 and a(3)=5 the entries are either {-4, -2, 2, 4} and occur in roughly equal ratios. - Robert G. Wilson v, Nov 04 2016

LINKS

Table of n, a(n) for n=1..71.

FORMULA

a(n) = 5 - A007652(n). - Robert G. Wilson v, Nov 04 2016

EXAMPLE

For n = 10 and prime(10) = 29, so a(10) = 5 - 9 = -4.

MATHEMATICA

f[n_] := 5 - Mod[Prime[n], 10]; Array[f, 71] (* Robert G. Wilson v, Nov 04 2016 *)

PROG

(PARI) a(n) = my(p=prime(n)); (10*(p\10)+5) - p; \\ Michel Marcus, Sep 30 2016

CROSSREFS

Cf. A007652, A184593.

Sequence in context: A129576 A122861 A326045 * A077814 A131728 A373088

Adjacent sequences: A277094 A277095 A277096 * A277098 A277099 A277100

KEYWORD

sign,easy

AUTHOR

Dimitris Valianatos, Sep 29 2016

STATUS

approved