cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A102205 Iccanobirt semiprimes (15 of 15): Semiprime numbers in A102125.

Original entry on oeis.org

4, 5071, 6313, 31591, 9853, 11733, 31865, 736481, 9834802, 5123383, 906334841, 312395329, 73044385753, 39216355244851, 353123779923181, 944016528715333, 901870160743125919, 3394064622591216338731, 798539095539570459224764519, 5844680137439021618014007903
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Crossrefs

Cf. A001358, A102125, A102185, A102191-A102204.

Programs

  • Mathematica
    nxt[{a_,b_,c_}]:=With[{ir=IntegerReverse},{b,c,ir[ir[a]+ir[b]+ir[c]]}]; Select[NestList[nxt,{0,0,1},200][[;;,1]],PrimeOmega[#]==2&] (* Harvey P. Dale, Jul 22 2025 *)

Formula

a(n) = A102125(A102185(n)).

Extensions

Offset changed to 1 and a(20) from Jinyuan Wang, Aug 14 2021

A102184 Iccanobirt semiprime indices (14 of 15): Indices of semiprime numbers in A102124.

Original entry on oeis.org

5, 11, 19, 22, 28, 29, 42, 61, 68, 72, 108, 120, 126, 211, 223, 281, 301, 308, 333, 344, 347, 363, 435, 462, 519, 538, 605
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Crossrefs

Cf. A001358, A102124, A102171-A102185, A102204.

Formula

A102124(a(n)) = A102204(n).

Extensions

a(14)-a(15) from Robert Price, Nov 10 2018
Offset changed to 1 and a(16)-a(27) from Jinyuan Wang, Aug 15 2021
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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