A145043 Primes p for which s=2 is the least positive integer such that sp-t(sp) is a triangular number, where t(n) is the maximal triangular number not exceeding n

5, 17, 23, 47, 53, 71, 73, 127, 173, 233, 251, 269, 281, 347, 353, 359, 431, 487, 491, 509, 541, 563, 569, 593, 613, 677, 743, 773, 827, 857, 863, 883, 929, 953, 977, 1013, 1153, 1187, 1283, 1319, 1361, 1373, 1439, 1481, 1583, 1613, 1619, 1709, 1871, 1997

Offset

1,1

Links

Table of n, a(n) for n=1..50.

Prog

(PARI) maxt(n) = {k = 1; while ((t=k*(k+1)/2) < n, k++); if (t == n, t, k--; k*(k+1)/2); }
lista(nn) = {forprime(p = 2, nn, if (! ispolygonal(p - maxt(p), 3) && ispolygonal(2*p - maxt(2*p), 3), print1(p, ", "); ); ); } \\ Michel Marcus, Jul 25 2014

Crossrefs

Cf. A000217, A145032, A145016, A145022, A145023.

Sequence in context: A236119 A141275 A303193 * A097434 A106012 A230527

Adjacent sequences: A145040 A145041 A145042 * A145044 A145045 A145046

Keyword

nonn

Author

Vladimir Shevelev, Sep 30 2008

Extensions

More terms from Michel Marcus, Jul 25 2014

Status

approved