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A038853 Numbers that are divisible by 5 and are the difference between two (different positive) cubes in at least one way. 2
215, 335, 485, 665, 875, 1115, 1330, 1385, 1685, 1720, 2015, 2170, 2375, 2680, 2765, 3185, 3250, 3635, 3880, 4095, 4115, 4570, 4625, 4905, 5165, 5320, 5735, 5805, 6130, 6335, 6795, 6965, 7000, 7625, 7875, 7930, 8315, 8920, 9035, 9045, 9260, 9785, 9970 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

FORMULA

A number is in this sequence iff it is of the form (k+5j)^3-k^3, where k,j are any positive integers, since (k+d)^3 - k^3 = d(3(k+d/2)^2+d^2/4) = 0 (mod 5) iff d=0 (mod 5), since 3x^2 =-y^2/4 (mod 5) iff x=y=0 (mod 5). - M. F. Hasler, Jun 07 2007

PROG

(PARI) A038853(Nmax=10^4, a=[]) = { local(t, j5); for(j=1, Nmax^(1/3)/5, j5=5*j; for(k=1, sqrt((Nmax/j5-j5^2-3*j5)/3), if(Nmax<t=(k+j5)^3-k^3, next); a=concat(a, t))); vecsort(a) } - M. F. Hasler, Jun 07 2007

CROSSREFS

Sequence in context: A181008 A191943 A046011 * A038860 A120536 A043391

Adjacent sequences:  A038850 A038851 A038852 * A038854 A038855 A038856

KEYWORD

nonn

AUTHOR

Jeff Burch

EXTENSIONS

Corrected by M. F. Hasler, Jun 07 2007

STATUS

approved

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Last modified August 20 03:34 EDT 2017. Contains 290823 sequences.