

A054254


a(n) is n plus the minimum of the a(i)*a(ni) of the previous i=1..n1.


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
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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(nk) if k<=n<=2k and n(n+1)/ 2k(k1) 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+n4)/2 =A034856(n1) =A000217(n)2 =A000297(n3)A000297(n2). For n>4: a(n)=a(n1)+n.
G.f.: x*(x^2x+1)*(x^3x^21)/(x1)^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 n1 do if procname(i)*procname(ni) < j then j := procname(i)*procname(ni); 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



