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A271183 Löschian numbers (A003136) k such that k + 1 is also Löschian number. 1
0, 3, 12, 27, 36, 48, 63, 75, 108, 111, 147, 156, 171, 192, 228, 243, 291, 300, 324, 336, 363, 372, 387, 399, 432, 468, 507, 576, 588, 603, 624, 651, 675, 687, 723, 732, 756, 768, 831, 867, 876, 948, 972, 975, 1008, 1083, 1092, 1116, 1200, 1227, 1236, 1251, 1263, 1296, 1299, 1323, 1332, 1371 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

May be called lesser of twin Löschian pairs.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

3 is a term because 3 = 1^2 + 1*1 + 1^2 and 3 + 1 = 4 = 0^2 + 0*2 + 2^2.

MATHEMATICA

Select[Range[0, 1400], AllTrue[{#, # + 1}, Resolve[Exists[{x, y}, Reduce[# == x^2 + x y + y^2, {x, y}, Integers]]] &] &] (* Version 10, or *)

Select[Range[0, 1400], Times @@ Boole@ Map[Resolve[Exists[{x, y}, Reduce[# == x^2 + x y + y^2, {x, y}, Integers]]] &, {#, # + 1}] == 1 &]  (* Michael De Vlieger, Apr 01 2016 *)

PROG

(PARI) has(n) = #bnfisintnorm(bnfinit(z^2+z+1), n);

print1(0, ", "); for(n=1, 2000, if(has(n) && has(n+1), print1(n, ", ")));

CROSSREFS

Cf. A003136.

Sequence in context: A110859 A190904 A345960 * A125614 A061936 A074630

Adjacent sequences:  A271180 A271181 A271182 * A271184 A271185 A271186

KEYWORD

nonn

AUTHOR

Altug Alkan, Apr 01 2016

STATUS

approved

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Last modified July 29 17:41 EDT 2021. Contains 346346 sequences. (Running on oeis4.)