0,2

a := proc(n) option remember; if n = -1 then -1 else 6*(6*n - 1)*(6*n + 1)*a(n - 1)/((n + 1)*(2*n + 1)) fi; end;

Sequence in context: A076715 A029549 A087639 this_sequence A099788 A126676 A073100

Adjacent sequences: A028347 A028348 A028349 this_sequence A028351 A028352 A028353

sign

N. J. A. Sloane (njas(AT)research.att.com).