OFFSET
1,11
MATHEMATICA
a[n_]:=a[n]=1-Sum[Times@@a/@y, {y, Select[IntegerPartitions[n], Length[#]>1&&OddQ[Length[#]]&]}];
Array[a, 40]
CROSSREFS
KEYWORD
sign
AUTHOR
Gus Wiseman, Mar 13 2018
STATUS
approved