A381921 Factorial numbers whose Hamming weight is also a factorial number.

1, 2, 6, 24, 5040, 40320, 362880, 1982608315404440064116146708361898137544773690227268628106279599612729753600000000000000, 126886932185884164103433389335161480802865516174545192198801894375214704230400000000000000

Offset: 1

Author

Ctibor O. Zizka, Mar 10 2025

Keywords

• nonn
• base

Examples

			k = 7:  A000120(A000142(7)) = 6, 6 is from A000142, thus 7! is a term.
		

Crossrefs

Cf. A000120, A000142, A381922.

Programs

Mathematica

With[{f = Range[100]!}, Select[f, MemberQ[f, DigitCount[#, 2, 1]] &]] (* Amiram Eldar, Mar 10 2025 *)

Formula

a(n) = A000142(A381922(n)).