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

Author

Shyam Sunder Gupta, Nov 11 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A005100, A231623, A228844.

Programs

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