

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
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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, n1, if (issquare(i) && issquare(ni), print1(n, ", ")))) \\ Michel Marcus, Nov 30 2013
(PARI) list(lim)=my(v=List()); for(n=2, lim, for(k=1, sqrtint(n1), if(issquare(nk^2), listput(v, n)))); Vec(v) \\ Charles R Greathouse IV, Dec 01 2013


CROSSREFS

Cf. A000404, A001105, A025285, A025302.
Sequence in context: A153162 A168199 A251736 * 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



