1,2

It would appear that a(n)=2^m-1 if 2n+1 is prime.

a(n)=sum{k=0..n, abs(Jacobi(n-k, 2k+1))2^k}

Cf. A005097, A110437.

Sequence in context: A006978 A060424 A119962 this_sequence A126879 A155128 A077314

Adjacent sequences: A110433 A110434 A110435 this_sequence A110437 A110438 A110439

easy,nonn

Paul Barry (pbarry(AT)wit.ie), Jul 20 2005