A228806 Smallest odd number greater than any previous term such that it divides the concatenation of all the previous terms and itself; begin with 1.

1, 5, 15, 25, 29, 35, 125, 625, 2125, 2675, 3125, 15625, 20125, 21875, 23975, 24797, 25125, 36875, 47495, 47725, 51875, 53125, 78125, 135475, 390625, 1171875, 1903875, 1928595, 2142375, 2265625, 6617125, 8385625, 8790525, 8807085, 8818575, 10504785

Offset

1,2

Comments

Terms not congruent to 0 (mod 5) are: 1, 29, 24797, 24848081, 91381387, 274144161, ..., .

Terms not congruent to 0 (mod 25) are: 1, 5, 15, 29, 35, 24797, 47495, 1928595, 8807085, 10504785, 24848081, 91381387, 274144161, ..., .

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..55

Example

a(5) equals 29 because 15152527 (mod 27) == 19, but 15152529 (mod 29) == 0.

Mathematica

f[s_List] := Block[{k = s[[-1]] + 2, conc = FromDigits[ Flatten@ IntegerDigits@ s]}, While[ Mod[ conc*10^Floor[ Log[10, k] + 1] + k, k] != 0, k += 2]; Append[s, k]]; Nest[f, {1}, 25]

Crossrefs

Cf. A171785.

Sequence in context: A066548 A075359 A190971 * A075336 A031236 A011535

Adjacent sequences: A228803 A228804 A228805 * A228807 A228808 A228809

Keyword

nonn,base

Author

Robert G. Wilson v, Sep 04 2013

Status

approved