A396487 Numbers with exactly one representation as the sum of two distinct upper twin primes.

12, 18, 20, 24, 26, 32, 36, 38, 44, 48, 56, 62, 66, 68, 78, 86, 108, 110, 114, 128, 140, 144, 156, 176, 186, 188, 198, 204, 218, 230, 234, 246, 266, 276, 278, 288, 308, 318, 354, 362, 416, 426, 438, 446, 458, 468, 488, 528, 548, 560, 576, 606, 608, 624, 638, 648, 666, 668, 686, 728, 740, 758, 776

Offset

1,1

Comments

Numbers k such that there is exactly one pair (p,q) with p < q, p and q in A006512, and p + q = k.

Includes 5 + p for all p > 5 in A006512. All other terms == 2 (mod 6).

Is a(484) = 24536 the largest term == 2 (mod 6)?

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(3) = 20 is a term because 20 = 7 + 13 and there is no other pair of distinct members of A006512 whose sum is 20.

Maple

N:= 1000: # for terms <= N
P:= select(t -> isprime(t) and isprime(t-2), [5, seq(i, i=7..N, 6)]):
R:= sort(select(`<=`, [seq(seq(P[i]+P[j], i=1..j-1), j=1..nops(P))], N)):
J:= select(proc(i) i=1 or (R[i-1] < R[i] and R[i] < R[i+1]) end proc, [$1..nops(R)-1]):
R[J];

Crossrefs

Cf. A006512, A334160.

Sequence in context: A091196 A319229 A334160 * A271345 A007624 A036456

Adjacent sequences: A396483 A396484 A396486 * A396488 A396489 A396490

Keyword

nonn,new

Author

Robert Israel, May 28 2026

Status

approved