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 A202242 n such that the sum of digit !! of n equals the sum of d|n, 1

%I #11 Mar 30 2012 18:36:00

%S 14,56,28361,119507,191557,287039,691259,750889

%N n such that the sum of digit !! of n equals the sum of d|n, 1<d<n.

%C No further terms less than 10^8.

%C The double factorial n!! (A006882) of a positive integer n is the product of the positive integers <= n that have the same parity as n.

%e 56 is in the sequence because 5!! + 6!! = 15 + 48 = 63, and sum of the divisors 1< d< 56 = sigma(56) - 56 - 1 = 120 - 56 - 1 = 63.

%t Q[n_]:=Module[{a=Total[Rest[Most[Divisors[n]]]]}, a == Total[IntegerDigits[n]!!]]; Select[Range[2, 10^5], Q]

%Y Cf. A006882, A048050.

%K nonn,hard,base

%O 1,1

%A _Michel Lagneau_, Dec 16 2011

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Last modified April 17 17:01 EDT 2024. Contains 371765 sequences. (Running on oeis4.)