A255542 a(n) = number of prime factors of (3^n + 10).

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

Offset

0,5

Links

Zak Seidov, Table of n, a(n) for n = 0..151

Formula

a(n) = A001222(3^n+10).

Example

a(0)=1 because 3^0+10=11, prime;
a(4)=2 because 3^4+10=91=7*13, semiprime;
a(7)=3 because 3^7+10=2197=13*13*13, 3-almost prime;
a(10)=4 because 3^7+10=59059=7*11*13*59, 4-almost prime;
a(16)=5 because 3^16+10=43046731=7*13*23*131*157, 5-almost prime.

Mathematica

a[n_]:= PrimeOmega[3^n+10]

Prog

(PARI) a(n) = bigomega(3^n+10)

Crossrefs

Cf. A001222, A102907, A217137.

Sequence in context: A166363 A117470 A070786 * A117500 A297626 A206441

Adjacent sequences: A255539 A255540 A255541 * A255543 A255544 A255545

Keyword

nonn

Author

Zak Seidov, Feb 25 2015

Status

approved