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

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

Offset

1,1

Comments

No further terms less than 10^8.

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.

Links

Table of n, a(n) for n=1..8.

Example

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.

Mathematica

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

Crossrefs

Cf. A006882, A048050.

Sequence in context: A281200 A212341 A067326 * A041374 A070741 A022286

Adjacent sequences: A202239 A202240 A202241 * A202243 A202244 A202245

Keyword

nonn,hard,base

Author

Michel Lagneau, Dec 16 2011

Status

approved