A359289 - OEIS

A359289

Number of divisors of 4*n-2 of form 4*k+1.

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

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OFFSET

1,3

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A001826(4*n-2).

G.f.: Sum_{k>0} x^k/(1 - x^(4*k-2)).

G.f.: Sum_{k>0} x^(2*k-1)/(1 - x^(4*k-3)).

MAPLE

f:= n -> nops(select(t -> t mod 4 = 1, NumberTheory:-Divisors(4*n-2))):

map(f, [$1..100]); # Robert Israel, Jan 23 2026