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.

Previous Showing 11-15 of 15 results.

A333368 Primes of the form k*m^(k*m) - 1 with m > 1.

Original entry on oeis.org

3, 31, 191, 5119, 131071, 524287, 3758096383, 4353564671, 1356446145697, 1618481116086271, 2058911320946489, 1046695266054721074427023041, 847823165504324070285888664019, 5359447279004780799548150067050349330431, 2817103802133904744169307240538184064530443801964688726052818649087
Offset: 1

Views

Author

Eder Vanzei, Mar 17 2020

Keywords

Examples

			31 appears in this sequence because 31=2*2^(2*2)-1 and 31 is prime.

Links

Crossrefs

Cf. A000040, A050918.

Programs

  • PARI
    lista(nn) = {my(k, n=2, v=List([]), x=4, y); while(xJinyuan Wang, Mar 18 2020

Extensions

Corrected by Michel Marcus and Jinyuan Wang, Mar 17 2020

A137811 Number of digits in the n-th Woodall prime.

Original entry on oeis.org

1, 2, 3, 11, 25, 27, 37, 40, 78, 112, 119, 142, 157, 229, 251, 1603, 2339, 2874, 3731, 4768, 5690, 6920, 6930, 29725, 43058, 45468, 200815, 359799, 382007, 441847, 606279, 712818, 1129757, 5122515
Offset: 1

Views

Author

Ant King, Feb 12 2008

Keywords

Comments

Woodall primes are prime numbers of the form k*2^k-1.

Examples

			As the sixth Woodall prime is a 27-digit number, we have a(6)= 27

Links

Crossrefs

Cf. A055642, A050918, A137716, A002234.

Programs

  • Mathematica
    IntegerLength/@Select[Table[n 2^n-1,{n,10000}],PrimeQ] (* The program generates the first 18 terms of the sequence. *) (* Harvey P. Dale, Feb 05 2023 *)

Formula

a(n) = A055642(A050918(n)).

Extensions

a(28)-a(34) from Amiram Eldar, Jul 19 2025

A172297 Partial sums of A002234.

Original entry on oeis.org

2, 5, 11, 41, 116, 197, 312, 435, 684, 1046, 1430, 1892, 2404, 3155, 3977, 9289, 17044, 26575, 38954, 54776, 73661, 96632, 119637, 218363, 361381, 512404, 1179475, 2374678, 3643657, 5111420, 7125412, 9493318, 13246266, 30262868
Offset: 1

Views

Author

Jonathan Vos Post, Jan 30 2010

Keywords

Comments

The subsequence of primes in this sequence begins: 2, 5, 11, 41, 197, 218363, 3643657.

Examples

			a(6) = 2 + 3 + 6 + 30 + 75 + 81 = 197.

Crossrefs

Cf. A000040, A002234, A050918.

Formula

a(n) = Sum_{i=1..n} {i such that the Woodall number i*2^i - 1 is prime}.

Extensions

a(34) added from the data at A002234 by Amiram Eldar, Jul 22 2025

A182342 Primes of the form n*2^n + 5.

Original entry on oeis.org

5, 7, 13, 29, 389, 2053, 49157, 106501, 402653189, 1744830469, 2473901162501, 184717953466373, 774056185954309, 31057439705591620336669228531717, 70745044697537026438728012485623813
Offset: 1

Views

Author

Patrick Devlin, Apr 25 2012

Keywords

Comments

These are similar to the Woodall primes, A050918, which are primes of the form n*2^n - 1.

Examples

			5 = 0*2^0 + 5; 7 = 1*2^1 + 5; 13 = 2*2^2 + 5; 29 = 3*2^3 + 5; 389 = 6*2^6 + 5

Crossrefs

Cf. A050918, A182354, A182352, A182353.

Programs

  • Maple
    #choose N large, then S is the desired set
f:=n->n*2^n + 5:
S:={}:
for n from 0 to N do if(isprime(f(n))) then S:=S union {f(n)}: fi: od

A182374 Primes of the form n*3^n + 1.

Original entry on oeis.org

19, 52489, 59296646043258913, 3140085798164163223281069127, 281013956365219695455558985684629594690518822413326510467
Offset: 1

Views

Author

Patrick Devlin, Apr 26 2012

Keywords

Comments

Similar to A060353, and to the Woodall primes A050918.

Examples

			19 = 2*3^2 + 1; 52489 = 8*3^8 + 1; a(3) = 32*3^32 + 1; a(4) = 54*3^54 + 1.

Crossrefs

Cf. A060353, A050918.

Programs

  • Maple
    #choose N large, then S is the desired set
f:=n->n*3^n + 1:
S:={}:
for n from 0 to N do if(isprime(f(n))) then S:=S union {f(n)}: fi: od
  • Mathematica
    Select[Table[n*3^n + 1, {n, 0, 580}], PrimeQ] (* Jayanta Basu, Jun 01 2013 *)
Previous Showing 11-15 of 15 results.

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