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A174245 a(n) is the smallest number m such that the sum of the first m squares ends in n '0's. 0
4, 24, 624, 5312, 45312, 445312, 6445312, 12890624, 212890624, 1787109375, 40893554687, 40893554687, 81787109375, 59918212890624, 129959106445312, 3740081787109375, 56259918212890624, 128129959106445312 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..18.

EXAMPLE

The smallest sum of squares ending in a zero is 1^2+2^2+3^2+4^2=30, so a(1)=4. Likewise, 1^2+...24^2=4900, so a(2)=24.

PROG

(PARI) sos(x) = (x)*(x+1)*(2*x+1)/6; a(p)={ local(s5=polrootspadic(sos(x), 5, p), s2=polrootspadic(sos(x), 2, p), ss10=Set()); for(i2=1, length(s2), v2=lift(s2[i2]); if(denominator(v2)==1, m2=Mod(v2, 2^p); for(i5=1, length(s5), s10=lift(chinese(m2, Mod(s5[i5], 5^p))); if(s10!=0&&sos(s10)%(10^p)==0, ss10=setunion(ss10, Set(s10))) ) ) ); ss10 }

CROSSREFS

Sequence in context: A211215 A249028 A216092 * A228191 A012989 A058171

Adjacent sequences:  A174242 A174243 A174244 * A174246 A174247 A174248

KEYWORD

base,nonn

AUTHOR

Phil Carmody, Mar 13 2010

EXTENSIONS

Typo in definition corrected by Zak Seidov, Mar 16 2010

STATUS

approved

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Last modified May 17 12:55 EDT 2021. Contains 343971 sequences. (Running on oeis4.)