A031884 Smaller of a pair of consecutive lucky numbers with a gap of 2n.

1, 3, 15, 79, 141, 51, 787, 495, 171, 937, 903, 745, 2851, 1611, 1057, 3811, 5769, 4893, 8719, 10683, 9841, 24073, 9567, 28245, 25687, 3507, 26943, 35743, 44805, 51979, 64723, 23205, 50779, 51475, 264075, 155833, 238057, 178755, 143311, 400591

Offset

1,2

Comments

a(n) is the first occurrence of a difference of 2n between A000959(k+1) and A000959(k). - Robert G. Wilson v, May 12 2006

a(136) > 10^9. - Donovan Johnson, Dec 07 2011

Unknown terms a(166), a(176), a(178), a(182), and a(185) through a(209) are all greater than 10^10. - Kevin P. Thompson, Nov 24 2021

Links

Kevin P. Thompson, Table of n, a(n) for n = 1..165 (terms 1..135 from Donovan Johnson)

Kevin P. Thompson, Table of n, a(n) for n = 1..210 with unknown terms

Example

a(4) = 79 since the lucky numbers A000959(20) = 79 and A000959(21) = 87 are the first consecutive pair with difference 2*4 = 8.

Mathematica

lst = Range[1, 10^6, 2]; i = 2; While[ i <= (len = Length@lst) && (k = lst[[i]]) <= len, lst = Drop[lst, {k, len, k}]; i++ ]; f[n_] := Block[{k = 1}, While[t[[k + 1]] - t[[k]] != 2n, k++ ]; t[[k]]]; Array[f, 41] (* Robert G. Wilson v, May 12 2006 *)

Crossrefs

Cf. A000959, A031885, A031883, A031158, A031886, A031888, A031890, A031892, A031894, A031896, A031898, A031900, A031902.

Sequence in context: A298771 A298576 A299568 * A337284 A186942 A193913

Adjacent sequences: A031881 A031882 A031883 * A031885 A031886 A031887

Keyword

nonn,more

Author

Patrick De Geest

Extensions

More terms from Robert G. Wilson v, May 12 2006

Status

approved