A086372 First differences of A027349.

-1, 0, 1, -1, 1, -1, 1, 0, 0, 0, 0, 1, -1, 1, 0, 1, -1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 2, 0, 1, 0, 2, 1, 1, 0, 3, 1, 1, 1, 3, 2, 1, 2, 3, 3, 2, 2, 4, 5, 1, 4, 5, 5, 3, 5, 6, 7, 4, 6, 8, 9, 5, 8, 11, 10, 8, 10, 13, 13, 11, 12, 17, 17, 13, 16, 22, 19, 19, 20, 26, 26, 23, 25, 33, 32, 29

Offset: 1

Author

Ralf Stephan, Sep 06 2003

Keywords

• sign
• easy

Comments

Sequence has the same parity as A000041, the partition numbers, i.e. a(n) is congruent A040051(n) mod 2 (proved by James Sellers using generating functions).

Programs

PARI

a(n)=polcoeff((1-x)*prod(k=1,n,1+x^(2*k+1),1+x*O(x^n)),n)