A129281 a(1)=1; for n > 1, a(n) = a(n-1) + (the largest value of gcd(a(k),n) for 1 <= k <= n-1).

1, 2, 3, 5, 10, 13, 14, 16, 19, 29, 30, 36, 49, 63, 78, 94, 95, 113, 132, 142, 163, 185, 186, 198, 203, 229, 238, 252, 281, 311, 342, 358, 391, 425, 432, 468, 505, 543, 582, 592, 593, 635, 636, 680, 695, 718, 765, 813, 862, 887, 938, 990, 1043, 1097, 1152, 1180

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Example

For those k where 1 <= k <= 9, gcd(a(5),10) = 10 is the largest value for a gcd(a(k),10). So a(10) = a(9) + 10 = 29.
For those k where 1 <= k <= 11, gcd(a(11),12) = 6 is the largest value for a gcd(a(k),12). So a(12) = a(11) + 6 = 36.

Maple

a[1]:=1: for n from 2 to 70 do a[n]:=a[n-1]+max(seq(gcd(a[k], n), k=1..n-1)) od: seq(a[n], n=1..70); # Emeric Deutsch, Apr 13 2007

Mathematica

Fold[Append[#1, #1[[-1]] + Max@GCD[#1, #2]] &, {1}, Range[2, 56]] (* Ivan Neretin, Oct 24 2018 *)

Crossrefs

Cf. A129282.

Sequence in context: A241167 A083571 A123090 * A289536 A022426 A005677

Adjacent sequences: A129278 A129279 A129280 * A129282 A129283 A129284

Keyword

nonn

Author

Leroy Quet, Apr 07 2007

Extensions

More terms from Emeric Deutsch, Apr 13 2007

Status

approved