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Taxicab numbers that are sandwiched between semiprimes.
0

%I #34 May 18 2024 09:54:40

%S 4104,171288,1728216,2864288,2987712,2991816,3512808,3551112,9016488,

%T 10424232,12753160,13825728,14197248,36047592,43450344,43699392,

%U 49844032,63057960,72131904,75550088,85188096,92384712,107872128,107919000,110808000,117258678,119824488,132678000

%N Taxicab numbers that are sandwiched between semiprimes.

%C All terms are even numbers.

%e 4104 = 2^3 * 3^3 * 19 (between 4103 = 11 * 373 and 4105 = 5 * 821).

%e 171288 = 2^3 * 3^3 * 13 * 61 (between 171287 = 157 * 1091 and 171289 = 103 * 1663).

%e 1728216 = 2^3 * 3^5 * 7 * 127 (between 1728215 = 5 * 345643 and 1728217 = 617 * 2801).

%t Select[Import["https://oeis.org/A001235/b001235.txt", "Table"][[;; , 2]], # < 1.5*10^8 && PrimeOmega[# + {-1, 1}] == {2, 2} &] (* _Amiram Eldar_, May 16 2024 *)

%Y Cf. A001235, A001358.

%Y Subsequence of A371602.

%K nonn

%O 1,1

%A _Massimo Kofler_, May 16 2024