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

Offset: 1

Author

Dimitris Valianatos, Sep 29 2016

Keywords

• sign
• easy

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

Examples

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

Crossrefs

Cf. A007652, A184593.

Programs

Mathematica

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

PARI

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

Formula

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