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URL: https://oeis.org/A129645

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A129645
a(1) = 1; for n>1, a(n) = a(n-1)*b(n-1) + 1, where {b(k)} is the concatenated list of the ordered positive divisors of the terms of {a(k)}.
2
1, 2, 3, 7, 8, 25, 26, 183, 184, 369, 1477, 11817, 11818, 59091, 1477276, 1477277, 2954555, 38409216, 998639617, 998639618, 2995918855, 182751050156, 33443442178549, 33443442178550, 66886884357101, 267547537428405
OFFSET
1,2
EXAMPLE
The list of positive divisors of the terms of {a(k)} is (sequence A129646) 1; 1,2; 1,3; 1,7; 1,2,4,8; .... The n-th term of {a(k)} is a(n-1)*A129646(n-1) +1.
MAPLE
aklist := [] ;
A129645 := proc(n)
option remember;
global aklist ;
local prev;
if n = 1 then
return 1;
else
prev := procname(n-1) ;
sort([op(numtheory[divisors](prev))]) ;
aklist := [op(aklist), op(%)] ;
return prev*op(n-1, aklist)+1 ;
end if;
end proc:
seq(A129645(n), n=1..26) ; # R. J. Mathar, Aug 24 2013
MATHEMATICA
aklist = {};
a[n_] := a[n] = If[n == 1, 1, With[{prev = a[n-1]}, aklist = Join[aklist, Divisors[prev]]; prev*aklist[[n-1]]+1]];
Table[a[n], {n, 1, 26}] (* Jean-François Alcover, Jan 27 2024, after R. J. Mathar *)
CROSSREFS
Cf. A129646.
Sequence in context: A029790 A369350 A206725 * A324481 A112994 A056036
KEYWORD
nonn
AUTHOR
Leroy Quet, Apr 25 2007
EXTENSIONS
More terms from Sean A. Irvine, May 19 2010; corrected (based on the ordered lists of divisors) by Franklin T. Adams-Watters, Aug 24 2013
STATUS
approved