A110072 - OEIS

A110072

Numbers k such that k = sigma(d_1!!*d_2!!*...*d_j!!) where d_1 d_2 ... d_j is the decimal expansion of k.

1, 163800, 1547520, 81254720

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OFFSET

1,2

COMMENTS

No more terms up to 10^25. It is very probable that there is no greater term. - Robert Gerbicz, May 09 2008

No other terms below 10^45. - Max Alekseyev, Feb 19 2024

LINKS

EXAMPLE

81254720 is a term because 81254720 = sigma(8!!*1!!*2!!*5!!*4!!*7!!*2!!*0!!).

MATHEMATICA

Do[h = IntegerDigits[n]; l = Length[h]; If[n == DivisorSigma[1, Product[h[[k]]!!, {k, l}]], Print[n]], {n, 0, 100000000}]

CROSSREFS

KEYWORD

base,more,nonn

AUTHOR

STATUS

approved