A101764 Iccanobif semiprime indices: Indices of semiprime numbers in A014258.

8, 10, 13, 17, 23, 26, 28, 29, 31, 39, 42, 53, 55, 56, 73, 83, 94, 98, 101, 113, 114, 115, 121, 167, 217, 255, 266, 326, 327, 333, 367, 389, 397, 404, 409, 423, 425, 467, 497, 570, 631, 639, 749, 761

Offset

1,1

Comments

This sequence also includes 815, 862, 943, 1013, 1106, 1204, 1319, 1398, 1419, 1554, 1669, 1729, 1762, 1801, 1847, 1874, 1930, 1977, and 2123. It might or might not include 791, 927, 1022, 1027, 1110, 1129, 1307, 1558, 1662, 1694, 1723, 1747, 1850, 1934, 1954, 1978, 2014, 2069, and 2077, but the required factoring proved rather difficult. There are no further terms below 2123. - Lucas A. Brown, Nov 12 2022

Links

Table of n, a(n) for n=1..44.

Lucas A. Brown, A101764.py.

Mathematica

nxt[{a_, b_}]:={b, IntegerReverse[a+b]}; Flatten[Position[NestList[nxt, {0, 1}, 500][[All, 1]], _?(PrimeOmega[#]==2&)]]-1 (* Harvey P. Dale, Jun 05 2022 *)

Crossrefs

Cf. A001358, A001129, A014258, A014259, A014260, A101763, A101765, A101766.

Sequence in context: A167487 A010916 A275627 * A309065 A048591 A102615

Adjacent sequences: A101761 A101762 A101763 * A101765 A101766 A101767

Keyword

nonn,base,hard,more

Author

Jonathan Vos Post and Ray Chandler, Dec 15 2004

Extensions

Missing 367 inserted and new terms 570-761 added by Lucas A. Brown, Nov 12 2022

Status

approved