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A155138 a(n) = nonnegative value y such that (A155136(n), y) is a solution to the Diophantine equation x^3+28*x^2 = y^2. 2
0, 27, 48, 57, 48, 15, 48, 147, 288, 477, 720, 1023, 1392, 1833, 2352, 2955, 3648, 4437, 5328, 6327, 7440, 8673, 10032, 11523, 13152, 14925, 16848, 18927, 21168, 23577, 26160, 28923, 31872, 35013, 38352, 41895, 45648, 49617, 53808, 58227, 62880 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Agrees with A155137 except for omission of zero after a(6) = 15.
LINKS
FORMULA
a(n) = Abs((n-1)^3-28*(n-1)).
G.f.: 3*x*(9-20*x+9*x^2+32*x^5-30*x^6-8*x^7+10*x^8)/(1-x)^4.
EXAMPLE
(A155136(4), a(4)) = (-19, 57) is a solution: (-19)^3+28*(-19)^2 = -6859+10108 = 3249 = 57^2.
(A155136(8), a(8)) = (21, 147) is a solution: 21^3+28*21^2 = 9261+12348 = 21609 = 147^2.
MATHEMATICA
Abs[#^3-28#]&/@Range[0, 40] (* Harvey P. Dale, Aug 30 2016 *)
PROG
(Magma) [ Abs((n-1)^3-28*(n-1)): n in [1..41] ];
CROSSREFS
Sequence in context: A153260 A254209 A155137 * A031325 A090761 A090760
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Jan 21 2009
STATUS
approved

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Last modified June 23 13:32 EDT 2024. Contains 373648 sequences. (Running on oeis4.)