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

Author

Artur Jasinski, Dec 12 2007

Keywords

• nonn
• base

Comments

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

Examples

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

Links

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

Crossrefs

Cf. A002822, A037074, A007953, A136017.

Programs

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 *)

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

Formula

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

Extensions

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