A085367 Semiprimes that can be expressed as the sum or difference of two cubes: intersection of A001358 and A045980.

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

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: A022421 A075395 A352775 * A343560 A330395 A081267

Adjacent sequences: A085364 A085365 A085366 * A085368 A085369 A085370

Keyword

nonn

Author

Hugo Pfoertner, Jun 25 2003

Status

approved