A328019 Positions of 1 in A328018.

1, 7, 35, 119, 387, 1050, 2786, 7160, 17157, 39087, 78453, 167183, 344072, 697116, 1310344, 2455274, 4569557, 7758203, 13461761, 23063807, 39017035, 66702580, 106675941, 172270944, 274763136, 437839603, 693741098, 1044076002, 1596344378, 2414009807, 3653875720

Offset

1,2

Comments

Does a(n+1)/a(n) tend to 1 as n tends to infinity? - Rémy Sigrist, Nov 11 2019

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, PARI program for A328019

Formula

a(1) = 1; a(n + 1) = A092433(a(n)) for n > 0.

Example

A328018 starts like this: 1, 2, 3, 4, 5, 6, 1, 8, 9, 10, 11, 12, 13, 2, 15, 16, 3, 18, 19, 20, 4, 22, 23, 24, 25, 26, 5, 6, 29, 30, 31, 32, 33, 34, 1, 36, 8, 38, 39, 40.
This has 1's in positions 1, 7 and 35. Therefore, 1, 7 and 35 are in the sequence.

Mathematica

With[{s = Select[Range[10^6], Or[Mod[#, 7] == 0, DigitCount[#, 10, 7] > 0] &]}, Nest[Append[#, s[[#[[-1]] ]] ] &, {1}, 12]] (* Michael De Vlieger, Oct 17 2019 *)

Prog

(PARI) print1 (w=1", "); k=0; for (n=1, oo, if (n%7==0 || setsearch(Set(digits(n)), 7), if (w==k++, print1 (w=n", ")))) \\ Rémy Sigrist, Nov 11 2019
(PARI) See Links section.

Crossrefs

Cf. A092433, A328018.

Sequence in context: A325732 A124090 A250284 * A327243 A059595 A327385

Adjacent sequences: A328016 A328017 A328018 * A328020 A328021 A328022

Keyword

nonn,base

Author

Rens Reus and David A. Corneth, Oct 01 2019

Extensions

More terms from Rémy Sigrist, Nov 11 2019

Status

approved