A339625 a(n) is the number of ways to write 6*n = p + q with p a lesser twin prime (A001359) and q a greater twin prime (A006512).
0, 1, 2, 3, 2, 3, 2, 4, 2, 3, 2, 4, 4, 3, 4, 0, 4, 2, 6, 5, 2, 4, 2, 5, 4, 4, 4, 6, 2, 6, 2, 4, 6, 5, 12, 3, 6, 2, 4, 8, 6, 8, 8, 2, 6, 3, 6, 10, 4, 13, 2, 6, 4, 4, 10, 4, 10, 4, 6, 3, 4, 6, 10, 5, 8, 1, 0, 6, 2, 12, 4, 6, 6, 2, 10, 3, 10, 6, 6, 7, 2, 8, 4, 6, 6, 0, 6, 6, 6, 9, 2, 6, 2, 5, 6, 4
Offset: 1
Keywords
Examples
a(4)=3 because 6*4 = 24 = 5 + 19 = 11 + 13 = 17 + 7 where (5,7), (11,13) and (17,19) are twin prime pairs.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Programs
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Maple
N:= 600: # for a(1)..a(floor(N/6))) P:= select(isprime, {seq(i,i=3..N,2)}): T1:= sort(convert(P intersect map(`-`,P,2),list)): T2:= map(`+`,T1,2): V:= Vector(N): nT:= nops(T1): for i from 1 to nT do for j from 1 to nT do v:= T1[i]+T2[j]; if v > N then break fi; V[v]:= V[v]+1; od od: seq(V[6*i],i=1..N/6);
Comments