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

1,1

Comments

The lesser of the two factors is in A002373.

Links

Table of n, a(n) for n=1..54.

Example

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, ...

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 *)

Crossrefs

Cf. A046388.

Sequence in context: A015831 A275169 A063176 * A119101 A342806 A190662

Adjacent sequences: A083369 A083370 A083371 * A083373 A083374 A083375

Keyword

nonn

Author

Lekraj Beedassy, Jun 05 2003

Extensions

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

Status

approved