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A004434 Numbers that are the sum of 5 distinct nonzero squares. 9
55, 66, 75, 79, 82, 87, 88, 90, 94, 95, 99, 100, 103, 106, 110, 111, 114, 115, 118, 120, 121, 123, 126, 127, 129, 130, 131, 132, 134, 135, 138, 139, 142, 143, 144, 145, 146, 147, 148, 150, 151, 152, 154, 155, 156, 157, 158, 159, 160, 162, 163 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Paul T. Bateman, Adolf J. Hildebrand, and George B. Purdy, Sums of distinct squares, Acta Arithmetica 67 (1994), pp. 349-380.

Franz Halter-Koch, Darstellung natürlicher Zahlen als Summe von Quadraten, Acta Arithmetica 42 (1982), pp. 11-20.

Index entries for sequences related to sums of squares

Index entries for linear recurrences with constant coefficients, signature (2,-1).

FORMULA

a(n) = n + 124 for n > 121. [Charles R Greathouse IV, Jul 17 2011]

PROG

(PARI) upto(lim)=my(v=List(), tb, tc, td, te); for(a=5, sqrt(lim), for(b=4, min(a-1, sqrt(lim-a^2)), tb=a^2+b^2; for(c=3, min(b-1, sqrt(lim-tb)), tc=tb+c^2; for(d=2, min(c-1, sqrt(lim-tc)), td=tc+d^2; for(e=1, d-1, te=td+e^2; if(te>lim, break, listput(v, te))))))); vecsort(Vec(v), , 8) \\ Charles R Greathouse IV, Jul 17 2011

(Haskell)

a004434 n = a004434_list !! (n-1)

a004434_list = filter (p 5 $ tail a000290_list) [1..] where

   p k (q:qs) m = k == 0 && m == 0 ||

                  q <= m && k >= 0 && (p (k - 1) qs (m - q) || p k qs m)

-- Reinhard Zumkeller, Apr 22 2013

CROSSREFS

Cf. A003995, A004431, A004432, A004433, A224981, A224982, A224983, A000290.

Sequence in context: A043959 A285804 A269808 * A168109 A116055 A068898

Adjacent sequences:  A004431 A004432 A004433 * A004435 A004436 A004437

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)