A178564 Semiprimes of the form m*k such that (m-1)/(k+1)=prime.

14, 39, 65, 87, 95, 119, 155, 159, 215, 287, 335, 377, 395, 407, 447, 515, 519, 559, 623, 629, 671, 695, 779, 807, 879, 923, 951, 959, 1115, 1159, 1167, 1415, 1527, 1631, 1671, 1679, 1727, 1769, 1835, 1919, 1959, 2159, 2195, 2319, 2391, 2495, 2519, 3007, 3035

Offset

1,1

Links

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

Example

a(1)=14 because 14=7*2 and (7-1)/(2+1)=2=prime, a(2)=39 because 39=13*3 and (13-1)/(3+1)=3=prime.

Mathematica

mkpQ[n_]:=Module[{fs=Transpose[FactorInteger[n]][[1]]}, PrimeQ[ (Last[ fs]- 1)/(First[fs]+1)]]; With[{sps=Select[Range[3100], PrimeOmega[#] == 2&]}, Select[sps, mkpQ]] (* Harvey P. Dale, Jun 12 2013 *)

Crossrefs

Cf. A000040, A001358, A178379.

Sequence in context: A187086 A044091 A044472 * A051866 A162266 A368717

Adjacent sequences: A178561 A178562 A178563 * A178565 A178566 A178567

Keyword

nonn

Author

Juri-Stepan Gerasimov, May 29 2010

Extensions

Corrected and extended by R. J. Mathar and D. S. McNeil, May 31 2010

Status

approved