A073629 a(1) = 1; a(2) =2; a(3) = 3; a(n) = smallest number greater than the previous term such that the sum of four successive terms is a prime.

1, 2, 3, 5, 7, 8, 9, 13, 17, 20, 21, 25, 31, 32, 39, 47, 49, 56, 59, 63, 73, 74, 83, 87, 93, 96, 97, 103, 105, 114, 117, 121, 127, 134, 139, 141, 143, 146, 147, 151, 155, 160, 165, 167, 169, 172, 175, 185, 187, 192, 193, 197, 205, 214, 223, 235, 239, 240, 253, 259, 261

Offset

1,2

Links

Table of n, a(n) for n=1..61.

Example

a(4)=5 as 1+2+3+5=11 is prime, 1+2+3+4=10 composite

Mathematica

nxt[{a_, b_, c_}]:=Module[{k=c+1}, While[!PrimeQ[a+b+c+k], k++]; {b, c, k}]; Transpose[NestList[ nxt[#]&, {1, 2, 3}, 70]][[1]] (* Harvey P. Dale, Aug 29 2012 *)

Crossrefs

Cf. A073627, A073628.

Sequence in context: A001857 A091532 A108345 * A125716 A171614 A029601

Adjacent sequences: A073626 A073627 A073628 * A073630 A073631 A073632

Keyword

nonn

Author

Amarnath Murthy, Aug 08 2002

Extensions

Corrected and extended by Sam Alexander, Feb 26 2005

Status

approved