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A076520 n appears once if n is the sum of 2 nonzero squares in 1 way, twice if n is the sum of 2 squares in 2 ways, 3 times if n is the sum of 2 squares 3 ways etc. 0
2, 5, 5, 8, 10, 10, 13, 13, 17, 17, 18, 20, 20, 25, 25, 26, 26, 29, 29, 32, 34, 34, 37, 37, 40, 40, 41, 41, 45, 45, 50, 50, 50, 52, 52, 53, 53, 58, 58, 61, 61, 65, 65, 65, 65, 68, 68, 72, 73, 73, 74, 74, 80, 80, 82, 82, 85, 85, 85, 85, 89, 89, 90, 90, 97, 97, 98, 100, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..69.

Index entries for sequences related to sums of squares

FORMULA

Does limit n -> infinity a(n)/n exist?

Answer: Yes, and it is equal to 4/Pi. - Charles R Greathouse IV, Dec 01 2013

PROG

(PARI) lista(nn) = for (n=1, nn, for (i=1, n-1, if (issquare(i) && issquare(n-i), print1(n, ", ")))) \\ Michel Marcus, Nov 30 2013

(PARI) list(lim)=my(v=List()); for(n=2, lim, for(k=1, sqrtint(n-1), if(issquare(n-k^2), listput(v, n)))); Vec(v) \\ Charles R Greathouse IV, Dec 01 2013

CROSSREFS

Cf. A000404, A001105, A025285, A025302.

Sequence in context: A204237 A153162 A168199 * A014249 A168071 A145420

Adjacent sequences:  A076517 A076518 A076519 * A076521 A076522 A076523

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Nov 09 2002

EXTENSIONS

Typo in definition corrected by Michel Marcus, Dec 01 2013

STATUS

approved

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Last modified October 24 06:16 EDT 2014. Contains 248502 sequences.