A045957 Twin even-lucky-numbers: middle terms.

3, 5, 11, 19, 21, 35, 43, 51, 53, 69, 99, 101, 115, 117, 131, 139, 149, 171, 197, 213, 229, 245, 261, 299, 309, 325, 373, 387, 389, 419, 435, 437, 517, 523, 533, 547, 587, 597, 629, 643, 645, 707, 709, 715, 739, 741, 779, 869, 883, 885, 915, 963, 965, 995, 997, 1091

Offset: 1

Author

Felice Russo

Keywords

• nonn

Comments

Numbers k such that both k-1 and k+1 are even-lucky numbers (A045954). - Amiram Eldar, Mar 20 2024

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A045954, A045955, A045956.

Programs

Mathematica

evenLuckies[max_] := Module[{lst = Range[2, max, 2], i = 2, len}, While[i <= (len = Length@lst) && (k = lst[[i]]) <= len, lst = Drop[lst, {k, len, k}]; i++]; lst]; twinMid[max_] := Module[{s = evenLuckies[max]}, s[[Position[ Differences[s], 2] // Flatten]] + 1]; twinMid[1100] (* Amiram Eldar, Mar 20 2024, after Robert G. Wilson v at A045954 *)

Formula

a(n) = A045955(n) + 1 = A045956(n) - 1. - Amiram Eldar, Mar 20 2024