A138906 -id:A138906 - cp's OEIS frontend

A138907 a(n) = A138906(n) - A138905(n).

2, 14, 2, 74, 32, 2, 2, -94, -52, 482, -262, 578, 2, 590, 452, 386, -814, 326, 1598, 1202, 758, 530, -1516, 290, 602, -154, -1618, 2354, 2612, 1442, 2420, -3646, 794, 1430, 1472, -862, -220, 1142, 938, 2642, -2458, 3782, 4130, 3698, 1622, 5798, 3386, -3742, 2, 6002, -8566, -1246, 2864, 3566, 1322, 2690, 3764

Offset: 1

Zak Seidov, Apr 03 2008

sign

Cf. A138905, A138906.

a138906[n_]:=Module[{p=1,cnt=0},Until[cnt==n,If[Mod[Prime[p],6n]==1,cnt++];p++];Prime[p-1]];a138905[n_]:=Module[{p=1,cnt=0},Until[cnt==n,If[Mod[Prime[p],6n]==6n-1,cnt++];p++];Prime[p-1]];Table[a138906[n]-a138905[n],{n,57}] (* James C. McMahon, Jun 23 2025 *)

a(41) corrected by James C. McMahon, Jun 23 2025

A138905 a(n) is n-th prime == -1 (mod 6n).

Original entry on oeis.org

5, 23, 71, 167, 179, 431, 461, 863, 863, 839, 1583, 1511, 1949, 2099, 2339, 4127, 4283, 4751, 4673, 4919, 5669, 6599, 8693, 10079, 7349, 10607, 12149, 11087, 12527, 11159, 15809, 19583, 16829, 19583, 13859, 25703, 24197, 25307, 23633, 21839, 34439

Offset: 1

Zak Seidov, Apr 03 2008

nonn

			a(1) = 1st term in A007528 (Primes of form 6n-1)
a(2) = 2nd term in A068231 (Primes congruent to 11 (mod 12))
a(3) = 3rd term in A061242 (Primes of form 18n-1)
a(4) = 4th term in A134517 (Primes of form 24n-1)
a(5) = 5th term in A132236 (Primes congruent to 29 (mod 30))

David Radcliffe, Table of n, a(n) for n = 1..10000

Cf. A007528, A061242, A068231, A093871, A132236, A134517, A138906, A138907.

a[n_]:=Module[{p=1,cnt=0},Until[cnt==n,If[Mod[Prime[p],6n]==6n-1,cnt++];p++];Prime[p-1]];Array[a,41] (* James C. McMahon, Jun 22 2025 *)

cp's OEIS Frontend

A138907 a(n) = A138906(n) - A138905(n).

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