A132839 Largest terms a(n) forming a self-convolution 5th power of an integer sequence (A132840) such that: a(n) <= 5*a(n-1) for n>0 with a(0)=1.

1, 5, 25, 125, 625, 3121, 15605, 78025, 390125, 1950625, 9753123, 48765615, 243828075, 1219140375, 6095701875, 30478509371, 152392546855, 761962734275, 3809813671375, 19049068356875, 95245341784374, 476226708921870

Offset

0,2

Links

Table of n, a(n) for n=0..21.

Prog

(PARI) {a(n)=local(A, t, r=1); A=if(n==0, [1], vector(n, j, a(j-1))); if(n==0, r=1, t=a(n-1); if(denominator(Vec(Ser(concat(A, 5*t))^(1/5))[n+1])==1, r=5*t, if(denominator(Vec(Ser(concat(A, 5*t-1))^(1/5))[n+1])==1, r=5*t-1, if(denominator(Vec(Ser(concat(A, 5*t-2))^(1/5))[n+1])==1, r=5*t-2, if(denominator(Vec(Ser(concat(A, 5*t-3))^(1/5))[n+1])==1, r=5*t-3, r=5*t-4))))); r}

Crossrefs

Cf. A132840 (fifth-root); variants: A132831, A132835, A132837.

Sequence in context: A057831 A014946 A188580 * A206451 A291164 A216126

Adjacent sequences: A132836 A132837 A132838 * A132840 A132841 A132842

Keyword

nonn

Author

Paul D. Hanna, Sep 10 2007

Status

approved