The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A123886 a(0)=1. a(n) = a(n-1) + (number of earlier terms {i.e., terms a(0) through a(n-1)} that divide n). 2
 1, 2, 4, 5, 8, 10, 12, 13, 17, 18, 22, 23, 27, 29, 31, 33, 37, 39, 42, 43, 48, 49, 52, 54, 59, 61, 64, 66, 69, 71, 75, 77, 81, 83, 86, 88, 93, 95, 97, 100, 106, 107, 110, 112, 116, 118, 121, 122, 128, 130, 134, 136, 141, 142, 147, 149, 153, 154, 157, 159, 165, 167, 170 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS A.H.M. Smeets, Table of n, a(n) for n = 0..20000 EXAMPLE Among terms a(0) through a(5) there are two terms that divide 6: a(0)=1, a(1)=2. So a(6) = a(5) + 2 = 12. MAPLE A123886 := proc(maxn) local a, nexta, n, i ; a := [1] ; for n from 2 to maxn do nexta := op(n-1, a) ; for i from 1 to n-1 do if (n-1) mod op(i, a) = 0 then nexta := nexta +1 ; fi ; od ; a := [op(a), nexta] ; od ; RETURN(a) ; end: maxn := 100 : alist := A123886(maxn) : for i from 1 to maxn do printf("%d, ", op(i, alist)) ; end : # R. J. Mathar, Oct 21 2006 MATHEMATICA f[l_List] := Append[l, Last[l] + Length[Select[l, Mod[Length[l], # ] == 0 &]]]; Nest[f, {1}, 63] (* Ray Chandler, Oct 19 2006 *) PROG (Python) a, an, la = [1], 1, 1 print(la-1, an) while la < 63: ....dc, di = 0, 0 ....while di < la: ........if la%a[di] == 0: ............dc = dc+1 ........di = di+1 ....an = an+dc ....la, a = la+1, a+[an] ....print(la-1, an) # A.H.M. Smeets, Jan 25 2019 CROSSREFS Cf. A123885. Sequence in context: A112777 A188972 A047612 * A005242 A323976 A188975 Adjacent sequences:  A123883 A123884 A123885 * A123887 A123888 A123889 KEYWORD easy,nonn AUTHOR Leroy Quet, Oct 17 2006 EXTENSIONS Extended by Ray Chandler, Oct 19 2006 More terms from R. J. Mathar, Oct 21 2006 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 22 03:20 EDT 2021. Contains 347605 sequences. (Running on oeis4.)