A104214 Numbers n such that the sum of the digits of the n-th lower twin prime is prime.

1, 2, 3, 5, 6, 9, 11, 13, 14, 15, 16, 18, 19, 20, 24, 27, 29, 31, 32, 33, 35, 36, 37, 40, 43, 45, 48, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 69, 71, 74, 76, 77, 80, 82, 84, 85, 86, 87, 88, 91, 94, 97, 98, 99, 101, 103, 104, 106, 109, 111, 112, 115, 116, 117, 118, 121

Offset

1,2

Links

Table of n, a(n) for n=1..67.

Example

The 5th lower twin prime is 29. 2+9=11 a prime, so 5 is listed.
The 4th lower twin prime is 17. 1+7=8 so 4 is missing from the table.

Prog

(PARI) sdtwprime(n) = { local(x, y); for(x=1, n, y=sumdigits(twinl(x)); if(isprime(y), print1(x", ") ) ) } sumdigits(n) = \ The sum of the digits of n { local(x, j, s=0); x=digits(n); for(j=1, length(x), s+=x[j]; ); return(s) } digits(n) = \ The vector of the digits of n { return(eval(Vec(Str(n)))) }

Crossrefs

Sequence in context: A175007 A284685 A113238 * A349523 A355616 A046657

Adjacent sequences: A104211 A104212 A104213 * A104215 A104216 A104217

Keyword

easy,nonn,base

Author

Cino Hilliard, Mar 13 2005

Status

approved