A083372 Least number having exactly two odd prime factors that differ by 2n.

15, 21, 55, 33, 39, 85, 51, 57, 115, 69, 203, 145, 87, 93, 259, 185, 111, 205, 123, 129, 235, 141, 371, 265, 159, 413, 295, 177, 183, 469, 335, 201, 355, 213, 219, 553, 395, 237, 415, 249, 623, 445, 267, 1313, 679, 485, 291, 505, 303, 309, 535, 321, 327, 565

Offset: 1

Author

Lekraj Beedassy, Jun 05 2003

Keywords

• nonn

Comments

The lesser of the two factors is in A002373.

Examples

			We have a(4) = 33 because 33 = 3*11, with 11 - 3 = 2*4, the smallest number with this property. Others are 85 = 5*13, 209 = 11*19, 713 = 23*31, 1073 = 29*37, 3233 = 53*61, ...
		

Crossrefs

Cf. A046388.

Programs

Mathematica

f[n_] := Block[{p = 3}, While[ ! PrimeQ[p] || ! PrimeQ[p + 2n], p++ ]; p(p + 2n)]; Table[ f[n], {n, 1, 55}]
Table[#(#+2n)&/@Select[Prime[Range[2,100]],PrimeQ[#+2n]&,1],{n,60}]// Flatten (* Harvey P. Dale, May 26 2018 *)

Extensions

Edited and extended by Robert G. Wilson v, Jun 07 2003