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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 30 17:12 EDT 2020. Contains 337440 sequences. (Running on oeis4.)