A231624 Smallest sets of 3 consecutive deficient numbers in arithmetic progression. The initial deficient number is listed.

1, 2, 3, 7, 8, 9, 13, 14, 15, 17, 21, 25, 27, 31, 32, 33, 37, 39, 43, 44, 45, 49, 50, 51, 53, 57, 61, 62, 63, 67, 69, 73, 74, 75, 77, 81, 85, 87, 91, 92, 93, 97, 99, 101, 105, 109, 111, 115, 116, 117, 121, 122, 123, 127, 128, 129, 133, 134, 135, 137, 141

Offset

1,2

Links

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

Example

1, 2, 3 is the smallest set of 3 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 > 2, AppendTo[a, n - 2*cd]], m = 2; cd = n - z1]; z1 = n], {n, 3, 1000000}]; a

Crossrefs

Cf. A005100, A231623, A228844.

Sequence in context: A370902 A076682 A327224 * A194381 A047245 A070752

Adjacent sequences: A231621 A231622 A231623 * A231625 A231626 A231627

Keyword

nonn

Author

Shyam Sunder Gupta, Nov 11 2013

Status

approved