OFFSET
1,2
COMMENTS
Conjecture: Any term not among 1, 2, 1009, 15051, 15052, 21772 has the form 36*k^2-2 or the form 36*k^2-3, where k is a positive integer.
Note that this conjecture implies the conjecture in A258168 since neither 36*k^2-2 nor 36*k^2-3 can be a multiple of 5.
For more comments, see the linked message to Number Theory Mailing List.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..500
Zhi-Wei Sun, Re: A new conjecture involving p^2+q, a message to Number Theory Mailing List, May 30, 2015.
EXAMPLE
a(1) = 1 since none of 1,2,3,4 has the form p^2+q with p and q both prime.
a(2) = 2 since none of 2,3,4,5 has the form p^2+q with p and q both prime.
MATHEMATICA
n=0; Do[Do[If[PrimeQ[m+r-Prime[k]^2], Goto[aa]], {r, 0, 3}, {k, 1, PrimePi[Sqrt[m+r]]}]; n=n+1; Print[n, " ", m]; Label[aa]; Continue, {m, 1, 278781}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Jun 06 2015
STATUS
approved