A175120 - OEIS

A175120

a(1)=2. a(n) = the smallest prime p > a(n-1) such that p-a(n-1)-1 is composite.

2, 7, 17, 43, 53, 79, 89, 139, 149, 199, 227, 263, 313, 347, 373, 383, 409, 419, 541, 557, 593, 619, 641, 677, 727, 743, 769, 797, 823, 839, 983, 1009, 1019, 1069, 1091, 1117, 1151, 1187, 1213, 1223, 1249, 1259, 1381, 1409, 1459, 1481, 1531, 1553, 1579, 1601

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

A175121(n) = A175120(n+1) - A175120(n) - 1.

LINKS

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

MATHEMATICA

sp[n_]:=Module[{np=NextPrime[n], pa1}, pa1=np-n-1; While[PrimeQ[pa1] || pa1==1, np=NextPrime[np]; pa1=np-n-1]; np]; Join[{2}, NestList[sp, 7, 50]] (* Harvey P. Dale, Jan 10 2012 *)

CROSSREFS

A175118, A175121

Sequence in context: A347079 A370304 A375821 * A239357 A106910 A108479

Adjacent sequences: A175117 A175118 A175119 * A175121 A175122 A175123

KEYWORD

nonn

AUTHOR

Leroy Quet, Feb 14 2010

EXTENSIONS

Extended by R. J. Mathar, Feb 21 2010

STATUS

approved