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

Author

Jonathan Vos Post and Ray Chandler, Dec 15 2004

Keywords

• nonn
• base
• hard
• more

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

• Lucas A. Brown, A101764.py.

Crossrefs

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

Programs

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 *)

Extensions

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