OFFSET
1,1
COMMENTS
EXAMPLE
The terms (center), their binary indices (left), and their weakly decreasing prime indices (right) begin:
{2,3} 6 (2,1)
{1,2,3} 7 (4)
{2,4} 10 (3,1)
{1,2,4} 11 (5)
{1,3,4} 13 (6)
{2,3,4} 14 (4,1)
{2,5} 18 (2,2,1)
{1,2,5} 19 (8)
{2,3,5} 22 (5,1)
{1,2,3,5} 23 (9)
{4,5} 24 (2,1,1,1)
{1,4,5} 25 (3,3)
{2,4,5} 26 (6,1)
{1,2,4,5} 27 (2,2,2)
{3,4,5} 28 (4,1,1)
{2,3,4,5} 30 (3,2,1)
{1,2,3,4,5} 31 (11)
{1,6} 33 (5,2)
{2,6} 34 (7,1)
{1,2,6} 35 (4,3)
{1,3,6} 37 (12)
{2,3,6} 38 (8,1)
MATHEMATICA
prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
bix[n_]:=Join@@Position[Reverse[IntegerDigits[n, 2]], 1];
Select[Range[100], EvenQ[Total[bix[#]]+Total[prix[#]]]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 14 2024
STATUS
approved