A097655 Numbers n such that n = d_1!!*d_2!!*...*d_k!! where d_1 d_2 ... d_k is the decimal expansion of n.

1, 2, 3, 15, 18432, 75600, 276531978240000, 4810168001497883738112000, 215788176336727572480000000, 2178419737991700039289327133392896000000000000

Offset

1,2

Comments

All terms are of the form 2^i*3^j*5^k*7^l.

Links

Table of n, a(n) for n=1..10.

Example

18432 is in the sequence because 18432 = 1!!*8!!*4!!*3!!*2!!.

Mathematica

Do[h=IntegerDigits[n]; l=Length[h]; If[n==Product[h[[k]]!!, {k, l}], Print[n]], {n, 2000000000}]

Crossrefs

Cf. A097653, A097654, A097643, A102279.

Sequence in context: A203966 A167444 A292709 * A080749 A070973 A209593

Adjacent sequences: A097652 A097653 A097654 * A097656 A097657 A097658

Keyword

base,nonn

Author

Farideh Firoozbakht, Sep 10 2004

Extensions

More terms from Farideh Firoozbakht, Jan 08 2005

Status

approved