A264744 Exponent of the prime power A264734(n).

1, 1, 1, 2, 1, 2, 3, 1, 4, 1, 1, 1, 1

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 22 2015

Keywords

• nonn
• more
• less

Comments

Subsequence of A025474.

Examples

			a(9) = 4 is the exponent of 81 = A264734(9) = 3^4.
		

Crossrefs

Cf. A025474, A264734 (prime power k such that both k - 2 and k + 2 is a prime power).

Programs

Mathematica

t = Prepend[Select[Range@ 100000, AllTrue[{# - 2, #, # + 2}, PrimePowerQ] &], 3]; Flatten@ Map[Last, FactorInteger@ # &@ t, {2}] (* Michael De Vlieger, Dec 03 2015, Version 10 *)

PARI

is(k) = isprimepower(k) || k==1;
for(k=1, 1e6, if(is(k) && is(k+2) && is(k-2), print1(bigomega(k), ", "))) \\ Altug Alkan, Nov 23 2015