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.

A102143 Iccanobirt prime indices (13 of 15): Indices of prime numbers in A102123.

Original entry on oeis.org

4, 6, 7, 11, 55, 56, 69, 87, 109, 191, 314, 4579, 6281, 6400, 23256, 31648
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Comments

a(17) > 50000. - Robert Price, Nov 10 2018

Crossrefs

Cf. A000040, A102123, A102131-A102145.

Programs

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

Formula

A102123(a(n)) = A102163(n).

Extensions

a(13)-a(16) from Robert Price, Nov 10 2018
Offset changed to 1 by Jinyuan Wang, Aug 02 2021

A102163 Iccanobirt primes (13 of 15): Prime numbers in A102123.

Original entry on oeis.org

2, 7, 31, 761, 380372309031901, 398539497395051, 6619750198532765321, 895548435204819863285711, 324218089757469614354964262603, 6299327678849021718683330197124506131574064354457936929
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Comments

Next term is too large to include.

Crossrefs

Cf. A000040, A102123, A102143, A102151-A102165.

Formula

a(n) = A102123(A102143(n)).

Extensions

Offset changed to 1 by Jinyuan Wang, Aug 15 2021

A102183 Iccanobirt semiprime indices (13 of 15): Indices of semiprime numbers in A102123.

Original entry on oeis.org

5, 9, 12, 15, 16, 17, 19, 21, 25, 28, 33, 35, 37, 46, 61, 63, 70, 71, 81, 82, 89, 90, 100, 103, 106, 121, 133, 147, 204, 212, 220, 263, 293, 311
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Comments

No more terms through 200.

Crossrefs

Cf. A001358, A102123, A102171-A102185, A102203.

Formula

A102123(a(n)) = A102203(n).

Extensions

a(29)-a(31) from Robert Price, Nov 10 2018
Offset changed to 1 and a(32)-a(34) from Jinyuan Wang, Aug 15 2021

A102203 Iccanobirt semiprimes (13 of 15): Semiprime numbers in A102123.

Original entry on oeis.org

4, 26, 49, 1651, 44311, 38141, 45901, 990681, 8041777, 60558487, 8252802091, 1348187591, 11280376871, 49455591538, 1658081357516741, 15268848817955861, 6791980801494070261, 8278821177559776598, 759117158185214871379, 47088657278621730593201, 187491222710962870446779
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Keywords

Crossrefs

Cf. A001358, A102123, A102183, A102191-A102205.

Formula

a(n) = A102123(A102183(n)).

Extensions

Offset changed to 1 and more terms from Jinyuan Wang, Aug 15 2021

A102115 Iccanobirt numbers (5 of 15): a(n) = R(a(n-1)) + a(n-2) + R(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, 117, 779, 1138, 9801, 3204, 22135, 57415, 77633, 144214, 541549, 1123036, 7257201, 3095708, 21636315, 55486847, 104580673, 482935860, 247988412, 1073911003, 3317721397, 9220077878, 15106615327, 89503015162
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-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]+R[a[n-3]];Table[a[n], {n, 0, 40}]
nxt[{a_,b_,c_}]:={b,c,Total[FromDigits/@Reverse/@IntegerDigits[ {a,c}]]+b}; Transpose[NestList[nxt,{0,0,1},35]][[1]] (* Harvey P. Dale, Dec 19 2011 *)

Formula

A004086(a(n)) = A102123(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.

Content is available under The OEIS End-User License Agreement.