A176544 Primes of the form semiprime(k)/sum of digits of semiprime(k).

7, 37, 19, 67, 19, 19, 37, 37, 73, 37, 73, 337, 367, 163, 73, 109, 127, 73, 109, 163, 127, 181, 163, 433, 181, 163, 199, 181, 271, 163, 199, 199, 271, 271, 397, 307, 307, 487, 379, 541, 433, 577, 397, 271, 631, 433, 379, 487, 919, 1459, 541, 937, 811, 631, 991

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = p = A001358(n)/A175013(n).

a(n) = A001358(A176543(n))/A175013(A176543(n)). - R. J. Mathar, Apr 26 2010

Example

7 is a term because 7 = 21/(2+1);
37 is a term because 37 = 111/(1+1+1).

Maple

A175013 := proc(n) A007953(A001358(n)) ; end proc: A007953 := proc(n) add(d, d=convert(n, base, 10)) ; end proc: for n from 1 to 4000 do r := A001358(n)/A175013(n) ; if type(r, 'integer') then if isprime(r) then printf("%d, ", r) ; end if; end if; end do: # R. J. Mathar, Apr 26 2010

Mathematica

Select[#/Total[IntegerDigits[#]]&/@Select[Range[30000], PrimeOmega[#]==2&], PrimeQ] (* Harvey P. Dale, Aug 10 2023 *)

Crossrefs

Cf. A001358 (semiprimes), A007953 (sum of digits), A175013, A176543.

Sequence in context: A120106 A240274 A129737 * A281994 A246603 A043374

Adjacent sequences: A176541 A176542 A176543 * A176545 A176546 A176547

Keyword

nonn,base

Author

Juri-Stepan Gerasimov, Apr 20 2010

Extensions

More terms from R. J. Mathar, Apr 26 2010

Status

approved