A136050 Sum of digits of product of twin primes A037074.

6, 8, 8, 8, 26, 17, 26, 17, 8, 17, 17, 26, 26, 26, 17, 26, 35, 35, 26, 26, 8, 35, 26, 17, 26, 35, 44, 26, 17, 35, 35, 35, 35, 26, 35, 26, 17, 26, 26, 26, 17, 35, 26, 35, 26, 35, 26, 17, 26, 17, 35, 35, 26, 26, 35, 35, 26, 35, 26, 35, 26, 26, 26, 35, 26, 44, 35, 26, 26, 35, 44, 35

Offset

1,1

Comments

Conjecture: except for the initial term, each term is one less than a multiple of 9. - Harvey P. Dale, Dec 02 2016

Links

Harvey P. Dale, Table of n, a(n) for n = 1..5000

Formula

a(n) = A007953(A037074(n)). - Michel Marcus, Nov 04 2013

Example

The product of the first twin primes is 15=3*5, and sum of digits of 15 is 6.

Mathematica

a = {6}; Do[If[PrimeQ[6n - 1] && PrimeQ[6n + 1], c = IntegerDigits[36n^2 - 1]; b = Total[c]; AppendTo[a, b]], {n, 400}]; a
Total[IntegerDigits[Times@@#]]&/@Select[Partition[Prime[Range[500]], 2, 1], #[[2]]- #[[1]]==2&] (* Harvey P. Dale, Dec 02 2016 *)

Prog

(PARI) lista(nn) = for (x=1, nn, if(prime(x+1)-prime(x)==2, print1(sumdigits(prime(x)*prime(x+1)), ", "))); \\ Michel Marcus, Nov 04 2013

Crossrefs

Cf. A002822, A037074, A007953, A136017.

Sequence in context: A300897 A346289 A049110 * A281112 A229020 A113697

Adjacent sequences: A136047 A136048 A136049 * A136051 A136052 A136053

Keyword

nonn,base

Author

Artur Jasinski, Dec 12 2007

Extensions

First term a(1)=6 inserted by Michel Marcus, Nov 04 2013

Status

approved