A272910 - OEIS

%I #23 May 23 2016 22:09:18

%S 19,32,93,124,208,243,308,395,427,471,603,672,1057,1568,1892,2181,

%T 2223,2587,3040,3049,4037,4336,5232,5556,6196,6305,6643,8288,8748,

%U 10161,10185,10612,10985,12352,13741,14807,16021,17568,20352,20653,24080,27216,27867,31113,31869,32032,32500,36593

%N Numbers n such that (n-1)^3 + (n+1)^3 is a taxi-cab number (A001235).

%C Numbers n such that 2*n*(n^2+3) is a member of A001235.

%C 19 and 3049 are the only prime numbers in this sequence for n < 10^5.

%C How is the graph of second differences of this sequence?

%H Chai Wah Wu, <a href="/A272910/b272910.txt">Table of n, a(n) for n = 1..300</a>

%e 19 is a term because 18^3 + 20^3 = 13832 = 2^3 + 24^3.

%o (PARI) T = thueinit(x^3+1, 1);

%o isA001235(n) = my(v=thue(T, n)); sum(i=1, #v, v[i][1]>=0 && v[i][2]>=v[i][1])>1;

%o lista(nn) = for(n=1, nn, if(isA001235(2*n*(n^2+3)), print1(n, ", ")));

%Y Cf. A001235, A153976, A259836.

%K nonn

%O 1,1

%A _Altug Alkan_, May 09 2016