A231625 Smallest sets of 4 consecutive deficient numbers in arithmetic progression. The initial deficient number is listed.

1, 2, 7, 8, 13, 14, 31, 32, 43, 44, 49, 50, 61, 62, 73, 74, 91, 92, 99, 115, 116, 121, 122, 127, 128, 133, 134, 145, 146, 151, 152, 163, 164, 169, 170, 181, 182, 187, 188, 195, 211, 212, 219, 229, 230, 235, 236, 241, 242, 247, 248, 253, 254, 265, 266, 283

Offset

1,2

Links

Shyam Sunder Gupta, Table of n, a(n) for n = 1..5000

Example

1, 2, 3, 4 is the smallest set of 4 consecutive deficient numbers in arithmetic progression so 1 is in the list.

Mathematica

DefQ[n_] := DivisorSigma[1, n] < 2 n; m = 2; z1 = 2; cd = 1; a = {}; Do[If[DefQ[n], If[n - z1 == cd, m = m + 1; If[m > 3, AppendTo[a, n - 3*cd]], m = 2; cd = n - z1]; z1 = n], {n, 3, 1000000}]; a

Crossrefs

Cf. A005100, A231623, A228961, A231624.

Sequence in context: A329410 A246389 A329409 * A032927 A004717 A308918

Adjacent sequences: A231622 A231623 A231624 * A231626 A231627 A231628

Keyword

nonn

Author

Shyam Sunder Gupta, Nov 11 2013

Status

approved