A163630 Numbers such that the two adjacent integers are a prime and 7 times a prime.

20, 22, 36, 48, 78, 90, 132, 162, 258, 330, 372, 468, 498, 510, 678, 708, 720, 750, 762, 888, 918, 972, 1098, 1170, 1212, 1380, 1560, 1602, 1758, 1800, 1980, 2052, 2178, 2220, 2358, 2442, 2472, 2610, 2682, 2778, 2862

Offset: 1

Author

Juri-Stepan Gerasimov, Aug 02 2009

Keywords

• nonn

Examples

			a(2)=22 lies between 21=7*A000040(2) and 23=A000040(9).
a(3)=36 lies between 35=7*A000040(3) and 37=A000040(12).
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A000040, A163492.

Programs

Mathematica

prQ[n_] := Module[{a = n - 1, b = n + 1}, (PrimeQ[a] && PrimeQ[b/7]) || (PrimeQ[b] && PrimeQ[a/7])]; Select[Range[5000], prQ] (* G. C. Greubel, Jul 30 2017 *)

Extensions

20 inserted, 62 removed, 90 added etc. by R. J. Mathar, Aug 07 2009