A076406 Numbers whose digital sum is equal to the sum of primes from their smallest to largest prime factor.

2, 3, 5, 7, 98, 640, 735, 980, 2401, 2625, 2744, 4913, 5145, 6272, 6400, 9800, 9856, 14336, 27440, 33614, 36015, 58564, 62720, 64000, 94325, 98000, 98560, 143360, 188650, 232925, 252105, 274400, 298144, 336140, 401408, 405769, 465850, 570999

Offset

1,1

Links

Donovan Johnson, Table of n, a(n) for n = 1..500

Example

980 = 2*2*5*7*7 is here since 9+8 = 17 and 2+3+5+7 = 17.

Mathematica

okQ[n_]:=Module[{totidn=Total[ IntegerDigits[n]], fctrs, mn, mx}, fctrs= Transpose[FactorInteger[n]][[1]]; mn=Min[fctrs]; mx=Max[fctrs]; Total[Prime[Range[PrimePi[mn], PrimePi[mx]]]]==totidn];
Select[ Range[2, 10000], okQ] (* Harvey P. Dale *)

Crossrefs

Sequence in context: A068827 A289755 A318202 * A171050 A092909 A080437

Adjacent sequences: A076403 A076404 A076405 * A076407 A076408 A076409

Keyword

base,nonn

Author

Jason Earls, Nov 07 2002

Extensions

a(20)-a(38) from Donovan Johnson, Sep 24 2009

Status

approved