A156324 a(1)=0, a(n+1) is smallest nonprime >= a(n)+n.

0, 1, 4, 8, 12, 18, 24, 32, 40, 49, 60, 72, 84, 98, 112, 128, 144, 161, 180, 200, 220, 242, 264, 287, 312, 338, 364, 391, 420, 450, 480, 511, 543, 576, 610, 645, 681, 718, 756, 795, 835, 876, 918, 961, 1005, 1050, 1096, 1143, 1191, 1240, 1290, 1341, 1393, 1446

Offset

1,3

Links

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

Example

a(4) is the smallest nonprime >= a(3) + 3 = 4 + 3 = 7, hence a(4)=8.

Maple

A141468 := proc(n) option remember ; local a ; if n = 1 then 0 ; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od: fi; end: A156324 := proc(n) option remember ; local a; if n = 1 then 0; else for a from procname(n-1)+n-1 do if not isprime(a) then RETURN(a) ; fi; od: fi; end: seq(A156324(n), n=1..80) ; # R. J. Mathar, Feb 10 2009

Mathematica

nxt[{n_, a_}]:=Module[{k=0, c=a+n+1}, While[PrimeQ[c+k], k++]; {n+1, c+k}]; Transpose[NestList[nxt, {0, 0}, 60]][[2]] (* Harvey P. Dale, Dec 29 2015 *)

Crossrefs

Cf. A000040, A055496, A141468.

Sequence in context: A311635 A049621 A072511 * A311636 A311637 A311638

Adjacent sequences: A156321 A156322 A156323 * A156325 A156326 A156327

Keyword

nonn

Author

Juri-Stepan Gerasimov, Feb 08 2009

Extensions

Terms beginning at a(31) corrected by R. J. Mathar, Feb 10 2009

Status

approved