A078215 a(1) = 1; a(n) for n > 1 is the smallest multiple of a(n-1) that is a square and begins with n.

1, 25, 3025, 48400, 5856400, 6377619600, 771691971600, 840372557072400, 915165714651843600, 1057931566137531201600, 1152087475523771478542400, 1254623260845387140132673600, 1366284731060626595604481550400

Offset

1,2

Links

Table of n, a(n) for n=1..13.

Example

For n = 3 we have a(n-1) = a(2) = 25; 121*25 = 3025 is the smallest multiple of 25 that is a square and begins with 3, so a(3) = 3025.

Prog

(PARI) {print1(a=1, ", "); for(n=2, 13, k=floor(log(a)/log(10))+1; s=n; t=s+1; m=floor(log(s)/log(10))+1; d=k-m; s=s*10^d; t=t*10^d; b=1; while(b>0, q=floor(s/a); while(b>0&&(p=q*a)<t, if(p>=s&&issquare(p), print1(p, ", "); b=0, q++)); s=10*s; t=10*t); a=p)}

Crossrefs

Cf. A078216, A078815.

Sequence in context: A209850 A014797 A077519 * A075414 A226277 A013737

Adjacent sequences: A078212 A078213 A078214 * A078216 A078217 A078218

Keyword

base,nonn

Author

Amarnath Murthy, Nov 22 2002

Extensions

Edited and extended by Klaus Brockhaus, Dec 06 2002

Status

approved