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 A292313 Numbers that are the sum of three squares in arithmetic progression. 5
 75, 300, 507, 675, 867, 1200, 1875, 2028, 2523, 2700, 3468, 3675, 4107, 4563, 4800, 5043, 6075, 7500, 7803, 8112, 8427, 9075, 10092, 10800, 11163, 12675, 13872, 14700, 15987, 16428, 16875, 18252, 19200, 20172, 21675, 22707, 23763, 24300, 24843, 27075, 28227, 30000, 30603 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 FORMULA Sequence is 3*(distinct elements in A198385). Numbers of the form 3*m^2 where 2*m^2 is in A004431. - Chai Wah Wu, Oct 05 2017 EXAMPLE 75 = 1^2 + 5^2 + 7^2 = 1 + 25 + 49, with 25 - 1 = 49 - 25 = 24. 675 = 3^2 + 15^2 + 21^2 = 9 + 225 + 441, with 225 - 9 = 441 - 225 = 216. PROG (PARI) t=4; k=3; while(t<=13000, i=k; e=0; v=t+i; while(i>1&&e==0, if(issquare(v), m=3*t; e=1; print1(m, ", ")); i+=-2; v+=i); k+=2; t+=k) CROSSREFS Subsequence of A033428. Cf. A000290, A000378, A004431, A134422, A292309, A292310, A292314, A292316. Sequence in context: A258056 A174685 A158742 * A158765 A226741 A223078 Adjacent sequences:  A292310 A292311 A292312 * A292314 A292315 A292316 KEYWORD nonn AUTHOR Antonio Roldán, Sep 14 2017 STATUS approved

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