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

Author

Paul D. Hanna, Sep 10 2007

Keywords

• nonn

Crossrefs

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

Programs

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}