A102252 Slowest increasing sequence beginning with 1 whose digits satisfy the rule d*2.
1, 2, 4, 8, 16, 21, 24, 248, 481, 681, 6212, 16212, 42421, 242484, 842484, 8168168, 48168162, 121621216, 816212162, 1242421242, 4212162124, 24212424848, 42484842421, 242484842484, 816816848168, 1684842484816, 8168481681621
Offset: 1
Examples
Read a(5)=16, which produces first digit of a(6)=2 because 1*2=2 and second digit of a(6)=1 and first digit of a(7)=2 because 6*2=12.
Crossrefs
Cf. A061581.
Programs
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Mathematica
t = Flatten[ NestList[ Function[x, Flatten[ IntegerDigits[2IntegerDigits[ x]]]], 1, 17]]; a = 0; l = {}; Do[k = 1; While[fd = FromDigits[ Take[t, k]]; a >= fd, k++ ]; t = Drop[t, k]; AppendTo[l, fd]; a = fd, {n, 27}]; l (* Robert G. Wilson v, Feb 21 2005 *)
Formula
d*2, beginning with 1.
Extensions
More terms from Robert G. Wilson v, Feb 21 2005
Comments