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 A003995 Sum of (any number of) distinct squares: of form r^2 + s^2 + t^2 + ... with 0 <= r < s < t < ... 24
 0, 1, 4, 5, 9, 10, 13, 14, 16, 17, 20, 21, 25, 26, 29, 30, 34, 35, 36, 37, 38, 39, 40, 41, 42, 45, 46, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 68, 69, 70, 71, 73, 74, 75, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 93, 94, 95, 97 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (2,-1). FORMULA Exponents in expansion of (1+x)*(1+x^4)*(1+x^9)*(1+x^16)*(1+x^25)*(1+x^36)*(1+x^49)*(1+x^64)*(1+x^81)*(1+x^100)*(1+x^121)*(1+x^144)*... For n > 98, a(n) = n + 30. - Charles R Greathouse IV, Sep 02 2011 (This implies a(n+2) = 2*a(n+1)-a(n) for n > 98.) MATHEMATICA lim = 10; s = {0}; Do[s = Union[s, s + n^2], {n, lim}]; Select[s, 0 <= # <= lim^2 &] (* T. D. Noe, Jul 10 2012 *) PROG (PARI) a(n)=if(n<1, 0, n=a(n-1); until(polcoeff(prod(k=1, sqrt(n), 1+x^k^2), n), n++); n) (Haskell) a003995 n = a003995_list !! (n-1) a003995_list = filter (p a000290_list) [0..]    where p (q:qs) m = m == 0 || q <= m && (p qs (m - q) || p qs m) -- Reinhard Zumkeller, Apr 22 2013 CROSSREFS Cf. A001983, A033461, A008935. Complement of A001422. Cf. A000290; subsequences: A004431, A004432, A004433, A004434, A224981, A224982, A224983. Sequence in context: A109825 A193259 A008935 * A064473 A287962 A001983 Adjacent sequences:  A003992 A003993 A003994 * A003996 A003997 A003998 KEYWORD nonn,easy,nice AUTHOR STATUS approved

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Last modified September 20 03:51 EDT 2019. Contains 327210 sequences. (Running on oeis4.)