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A054254 a(n) is n plus the minimum of the a(i)*a(n-i) of the previous i=1..n-1. 2
0, 1, 2, 5, 8, 13, 19, 26, 34, 43, 53, 64, 76, 89, 103, 118, 134, 151, 169, 188, 208, 229, 251, 274, 298, 323, 349, 376, 404, 433, 463, 494, 526, 559, 593, 628, 664, 701, 739, 778, 818, 859, 901, 944, 988, 1033, 1079, 1126, 1174, 1223, 1273 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

If in the Maple code "if n<=2 then n" was replaced by "if n<=1 then n", then the sequence would become the triangular numbers A000217. In general, if the Maple code was "if n<=k then n" for some given k >0 then a(n) would be n if n<=k, n+k(n-k) if k<=n<=2k and n(n+1)/ 2-k(k-1) if 2k<=n. - Henry Bottomley, Mar 30 2001

LINKS

Table of n, a(n) for n=0..50.

FORMULA

For n>3: a(n) =(n^2+n-4)/2 =A034856(n-1) =A000217(n)-2 =A000297(n-3)-A000297(n-2). For n>4: a(n)=a(n-1)+n.

G.f.: x*(x^2-x+1)*(x^3-x^2-1)/(x-1)^3 [R. J. Mathar, Dec 09 2009]

EXAMPLE

a(3)=3+1*2=5, a(4)=4+2*2=8 since 2*2<1*5, a(5)=5+1*8=13 since 1*8<2*5.

MAPLE

A054254 := proc(n) local i, j; option remember; if n<=2 then n else j := 10^100; for i from 1 to n-1 do if procname(i)*procname(n-i) < j then j := procname(i)*procname(n-i); end if; end do; n+j; fi; end proc;

CROSSREFS

Sequence in context: A083704 A111097 A027916 * A025216 A076059 A299732

Adjacent sequences:  A054251 A054252 A054253 * A054255 A054256 A054257

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 04 2000

EXTENSIONS

More specific name from R. J. Mathar, Dec 09 2009

STATUS

approved

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Last modified January 16 23:44 EST 2019. Contains 319206 sequences. (Running on oeis4.)