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A292313
Numbers that are the sum of three squares in arithmetic progression.
6
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
OFFSET
1,1
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
KEYWORD
nonn
AUTHOR
Antonio Roldán, Sep 14 2017
STATUS
approved