A138980 a(0)=1; for n>=1, a(n) = smallest prime > a(n-1) such that (sum{k=0 to n} a(k)) is composite.

1, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281

Offset

0,2

Comments

Although superficially similar to A049561, the two sequences are in fact quite different (see for example A138982).

Links

R. J. Mathar, Apr 30 2008, Table of n, a(n) for n = 0..112

Maple

A138980 := proc(n) option remember ; local i, p ; if n = 0 then 1 ; else for p from nextprime(A138980(n-1)) do if isprime(p) then if not isprime( p+add(A138980(i), i=0..n-1) ) then RETURN(p) ; fi ; fi ; od: fi ; end: seq(A138980(n), n=0..120) ; # R. J. Mathar Apr 30 2008

Crossrefs

Cf. A138981, A138982, A049561.

Sequence in context: A322184 A245072 A338134 * A191378 A191376 A179429

Adjacent sequences: A138977 A138978 A138979 * A138981 A138982 A138983

Keyword

nonn

Author

Leroy Quet, Apr 05 2008

Extensions

More terms from R. J. Mathar, Apr 30 2008

Status

approved