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A038860
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Numbers ending with '5' that are the difference of two positive cubes.
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1
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215, 335, 485, 665, 875, 1115, 1385, 1685, 2015, 2375, 2765, 3185, 3635, 4095, 4115, 4625, 4905, 5165, 5735, 5805, 6335, 6795, 6965, 7625, 7875, 8315, 9035, 9045, 9785, 10305, 10565, 11375, 11655, 12215, 13085, 13095, 13985, 14625, 14915, 15875
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OFFSET
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1,1
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COMMENTS
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Contains (k+5(2j+1))^3-k^3 for any integers k,j>=0. - M. F. Hasler, May 31, 2007
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LINKS
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Table of n, a(n) for n=1..40.
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FORMULA
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A number is in this sequence iff it is of the form (k+10j-5)^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) == 5 (mod 10) iff d is odd and d == 0 (mod 5) (cf. A038853) - M. F. Hasler, Jun 07 2007
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PROG
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(PARI) A038860(Nmax=20000, a=[]) = { local(t, j5); forstep( j=1, Nmax^(1/3)/5, 2, j5=5*j; for(k=1, sqrt((Nmax/j5-j5^2-3*j5)/3), if(Nmax<t=(k+j5)^3-k^3, break); a=concat(a, t))); vecsort(a) } \\ M. F. Hasler, Jun 07 2007
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CROSSREFS
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Intersection of A017329 and A181123.
Sequence in context: A191943 A046011 A038853 * A120536 A043391 A063358
Adjacent sequences: A038857 A038858 A038859 * A038861 A038862 A038863
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KEYWORD
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nonn,base
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AUTHOR
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Jeff Burch
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EXTENSIONS
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Corrected by M. F. Hasler, Jun 07 2007
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STATUS
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approved
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