

A100675


a(1) = 1; for n >= 1, a(n+1) = Sum_{k=1..n} gcd(k, a(n)).


2



1, 1, 2, 4, 8, 9, 10, 14, 18, 27, 22, 26, 18, 37, 14, 40, 56, 59, 18, 64, 56, 73, 22, 64, 68, 65, 70, 92, 78, 105, 126, 148, 64, 113, 34, 100, 140, 199, 38, 112, 170, 157, 42, 196, 154, 181, 46, 136, 168, 309, 82, 116, 132, 271, 54, 244, 112, 285, 254, 88, 238, 227, 62
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OFFSET

1,3


LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000


MAPLE

a[1]:=1: for n from 2 to 80 do b[n]:=[seq(gcd(k, a[n1]), k=1..n1)]: a[n]:=sum(b[n][j], j=1..nops(b[n])) od: seq(a[n], n=1..80);


MATHEMATICA

a[1] = 1; a[n_] := a[n] = Plus @@ GCD[Table[i, {i, n  1}], a[n  1]]; Table[ a[n], {n, 62}] (* Robert G. Wilson v, Dec 09 2004 *)
nxt[{n_, a_}]:={n+1, Total[GCD[Range[n], a]]}; NestList[nxt, {1, 1}, 70][[All, 2]] (* Harvey P. Dale, Sep 10 2019 *)


CROSSREFS

Sequence in context: A326713 A328945 A050907 * A196730 A325942 A325944
Adjacent sequences: A100672 A100673 A100674 * A100676 A100677 A100678


KEYWORD

nonn


AUTHOR

Leroy Quet, Dec 06 2004


EXTENSIONS

More terms from Emeric Deutsch and Robert G. Wilson v, Dec 09 2004
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 16 2007


STATUS

approved



