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A085367 Semiprimes that can be expressed as the sum or difference of two cubes: intersection of A001358 and A045980. 2
9, 26, 35, 65, 91, 133, 169, 215, 217, 218, 335, 341, 386, 407, 469, 485, 511, 559, 721, 737, 793, 817, 866, 973, 1027, 1115, 1141, 1241, 1261, 1267, 1339, 1343, 1385, 1387, 1538, 1603, 1685, 1727, 1843, 1853, 1981, 2071, 2189, 2402, 2413, 2611, 2743, 2771 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1)=9 because 2^3+1^3=3*3, a(2)=26=3^3-1^3=2*13.

a(5)=91 is the smallest semiprime expressible in two different ways: 91=4^3+3^3=6^3-5^3=7*13.

PROG

(PARI) T=thueinit('z^3+1);

is(n)=bigomega(n)==2 && #thue(T, n)

list(lim)=my(v=List()); forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), if(#thue(T, p*q), listput(v, p*q)))); Set(v) \\ Charles R Greathouse IV, Nov 29 2014

CROSSREFS

Cf. A001358, A045980, A085366.

Sequence in context: A255107 A022421 A075395 * A081267 A052153 A154560

Adjacent sequences:  A085364 A085365 A085366 * A085368 A085369 A085370

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Jun 25 2003

STATUS

approved

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Last modified February 17 17:59 EST 2020. Contains 331999 sequences. (Running on oeis4.)