

A136050


Sum of digits of product of twin primes A037074.


2



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
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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: A157683 A300897 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



