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 1-6 of 6 results.

A102142 Iccanobirt prime indices (12 of 15): Indices of prime numbers in A102122.

Original entry on oeis.org

4, 6, 7, 12, 19, 30, 37, 67, 93, 109, 297, 341, 602, 1377, 1745, 1972, 4208, 7942, 9572, 10409, 11927, 12707, 13460, 33803
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Comments

No more terms through 5000.
a(25) > 50000. - Robert Price, Nov 10 2018

Crossrefs

Cf. A000040, A102122, A102131-A102145.

Programs

  • Mathematica
    a[n_] := a[n] =
   IntegerReverse[IntegerReverse[a[n - 1]] + a[n - 2] + a[n - 3]];
a[0] = 0; a[1] = 0; a[2] = 1;
Select[Range[0, 5000], PrimeQ[a[#]] &] (* Robert Price, Apr 10 2020 *)

Formula

A102122(a(n)) = A102162(n).

Extensions

a(18)-a(24) from Robert Price, Nov 10 2018

A102162 Iccanobirt primes (12 of 15): Prime numbers in A102122.

Original entry on oeis.org

2, 7, 31, 67, 908821, 6171227123, 833416212437, 925518314049349041313, 366319426867272069390603006331, 41322662051354105860272734271998443
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Comments

Next term is too large to include.
The next term has 99 digits. - Harvey P. Dale, Sep 10 2024

Crossrefs

Cf. A000040, A102122, A102142, A102151-A102165.

Programs

  • Mathematica
    nxt[{a_,b_,c_}]:={b,c,IntegerReverse[IntegerReverse[c]+b+a]}; Select[NestList[nxt,{0,0,1},150][[;;,1]],PrimeQ] (* Harvey P. Dale, Sep 10 2024 *)

Formula

a(n) = A102122(A102142(n)).

Extensions

Offset changed to 1 by Jinyuan Wang, Aug 14 2021

A102182 Iccanobirt semiprime indices (12 of 15): Indices of semiprime numbers in A102122.

Original entry on oeis.org

5, 9, 11, 18, 21, 29, 31, 64, 69, 76, 80, 81, 102, 111, 112, 120, 122, 133, 135, 136, 187, 212, 219, 314
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Crossrefs

Cf. A001358, A102122, A102171-A102185, A102202.

Formula

A102122(a(n)) = A102202(n).

Extensions

a(22) from Robert Price, Nov 10 2018
Offset changed to 1 and a(23)-a(24) from Jinyuan Wang, Aug 14 2021

A102202 Iccanobirt semiprimes (12 of 15): Semiprime numbers in A102122.

Original entry on oeis.org

4, 26, 302, 6487, 6572211, 9962261161, 20114953831, 72323276790496009462, 9563112289639086692081, 639278857103151880047311, 13532727020275663728604021, 91820624869556443938377242, 629083300047263751187646851269521, 40032985928622992884587988549627831
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Crossrefs

Cf. A001358, A102122, A102182, A102191-A102205.

Formula

a(n) = A102122(A102182(n)).

Extensions

Offset changed to 1 and more terms from Jinyuan Wang, Aug 14 2021

A102114 Iccanobirt numbers (4 of 15): a(n) = R(a(n-1)) + a(n-2) + a(n-3), where R is the digit reversal function A004086.

Original entry on oeis.org

0, 0, 1, 1, 2, 4, 7, 13, 42, 44, 99, 185, 724, 711, 1026, 7636, 8104, 12680, 24361, 37126, 99214, 102786, 823541, 347328, 1750070, 1871440, 2539179, 13340862, 31214950, 21821254, 89768624, 95723002, 131622637, 921717757, 985062768
Offset: 0

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 30 2004

Keywords

Comments

Digit reversal variation of tribonacci numbers A000073.
Inspired by Iccanobif numbers: A001129, A014258-A014260.

Crossrefs

Cf. A102111-A102125.

Programs

  • Mathematica
    R[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Clear[a];a[0]=0;a[1]=0;a[2]=1;a [n_]:=a[n]=R[a[n-1]]+a[n-2]+a[n-3];Table[a[n], {n, 0, 40}]
nxt[{a_,b_,c_}]:={b,c,FromDigits[Reverse[IntegerDigits[c]]]+b+a}; Transpose[NestList[nxt,{0,0,1},40]][[1]]  (* Harvey P. Dale, May 30 2012 *)

Formula

A004086(a(n)) = A102122(n).

A102118 Iccanobirt numbers (8 of 15): a(n) = R(a(n-1) + a(n-2) + a(n-3)), where R is the digit reversal function A004086.

Original entry on oeis.org

0, 0, 1, 1, 2, 4, 7, 31, 24, 26, 18, 86, 31, 531, 846, 8041, 8149, 63071, 16297, 71578, 649051, 629637, 6620531, 9129987, 55108361, 97885807, 551421261, 924514407, 5741283751, 9149127127, 58252941851, 92725334137, 511304721061
Offset: 0

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 30 2004

Keywords

Comments

Digit reversal variation of tribonacci numbers A000073.
Inspired by Iccanobif numbers: A001129, A014258-A014260.

Links

Crossrefs

Cf. A102111, A102112, A102113, A102114, A102115, A102116, A102117, A102119, A102120, A102121, A102122, A102123, A102124, A102125.

Programs

  • Mathematica
    R[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Clear[a];a[0]=0;a[1]=0;a[2]=1;a [n_]:=a[n]=R[a[n-1]+a[n-2]+a[n-3]];Table[a[n], {n, 0, 40}]
Transpose[NestList[{#[[2]],#[[3]],FromDigits[Reverse[IntegerDigits[Total[ #]]]]}&,{0,0,1},40]][[1]] (* Harvey P. Dale, Dec 04 2012 *)

Extensions

Incorrect formula removed by Georg Fischer, Dec 18 2020
Showing 1-6 of 6 results.

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

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