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 1-4 of 4 results.

A378135 a(n) = p(n*p(n)), where p(x) = least prime > x.

Original entry on oeis.org

2, 3, 7, 17, 23, 37, 43, 79, 89, 101, 113, 149, 157, 223, 239, 257, 277, 331, 347, 439, 461, 487, 509, 673, 701, 727, 757, 787, 821, 907, 937, 1151, 1187, 1223, 1259, 1297, 1361, 1523, 1559, 1601, 1657, 1777, 1811, 2027, 2069, 2129, 2179, 2503, 2549, 2609, 2657
Offset: 0

Views

Author

Clark Kimberling, Nov 20 2024

Keywords

Examples

			p(0) = 2, so a(0) = p(0*p(0)) = 2.

Crossrefs

Cf. A000040, A013636, A151800, A378136, A378137.

Programs

  • Mathematica
    Table[NextPrime[n*NextPrime[n]], {n, 1, 80}]
  • PARI
    p(n) = nextprime(n+1);
a(n) = p(n*p(n)); \\ Michel Marcus, Nov 21 2024

Formula

a(n) = A151800(n*A151800(n)).

A171228 n^(p-n) where p is smallest prime > n.

Original entry on oeis.org

0, 1, 2, 9, 4, 25, 6, 2401, 512, 81, 10, 121, 12, 28561, 2744, 225, 16, 289, 18, 130321, 8000, 441, 22, 148035889, 7962624, 390625, 17576, 729, 28, 841, 30, 887503681, 33554432, 1185921, 39304, 1225, 36, 1874161, 54872, 1521, 40, 1681, 42, 3418801
Offset: 0

Views

Author

Juri-Stepan Gerasimov, Dec 05 2009

Keywords

Links

Crossrefs

Cf. A013632, A013636.

Programs

  • Mathematica
    Table[n^(NextPrime[n]-n),{n,0,50}] (* Harvey P. Dale, Jun 20 2013 *)

Extensions

Definition corrected by Andrew Weimholt, Dec 08 2009

A378136 a(n) = p(2*n*p(n)), where p(x) = least prime > x.

Original entry on oeis.org

2, 5, 13, 31, 41, 71, 89, 157, 179, 199, 223, 293, 313, 443, 479, 521, 547, 647, 691, 877, 929, 967, 1013, 1361, 1399, 1451, 1511, 1567, 1627, 1801, 1861, 2297, 2371, 2447, 2521, 2591, 2671, 3037, 3119, 3203, 3299, 3527, 3613, 4049, 4139, 4231, 4327, 4987, 5099
Offset: 0

Views

Author

Clark Kimberling, Nov 20 2024

Keywords

Examples

			p(0) = 2, so a(0) = p(2*p(0)) = 5.

Crossrefs

Cf. A000040, A013636, A151800, A378135.

Programs

  • Mathematica
    Table[NextPrime[2 n*NextPrime[n]], {n, 0, 80}]
  • PARI
    p(n) = nextprime(n+1);
a(n) = p(2*n*p(n)); \\ Michel Marcus, Nov 21 2024

A354881 Primes p such that, if q is the next prime, the digit reversal of p*q is prime.

Original entry on oeis.org

5, 31, 37, 41, 53, 103, 197, 263, 277, 337, 349, 353, 359, 373, 397, 401, 421, 431, 439, 547, 569, 587, 599, 857, 859, 863, 877, 883, 983, 1009, 1013, 1039, 1069, 1091, 1097, 1103, 1117, 1129, 1153, 1171, 1193, 1213, 1223, 1237, 1249, 1279, 1291, 1301, 1367, 1811, 1871, 1931, 1979, 2647, 2663
Offset: 1

Views

Author

J. M. Bergot and Robert Israel, Jul 13 2022

Keywords

Comments

Primes p such that A013636(p) is in A095179.

Examples

			a(3) = 37 is a term because 37 is prime, the next prime is 41, 37*41 = 1517 and its digit reversal 7151 is prime.

Links

Crossrefs

Cf. A013636, A004086, A095179.

Programs

  • Maple
    revdigs:= proc(n) local L,i;
  L:= convert(n,base,10);
  add(L[-i]*10^(i-1),i=1..nops(L))
end proc:
P:= [seq(ithprime(i),i=1..1000)]:
P[select(i -> isprime(revdigs(P[i]*P[i+1])), [$1..999])];
  • Mathematica
    a354881[n_] := Select[Map[Prime, Range[n]], PrimeQ[FromDigits[Reverse[IntegerDigits[# NextPrime[#]]]]]&]
a354881[390] (* Hartmut F. W. Hoft, Jul 20 2022 *)
Select[Partition[Prime[Range[400]],2,1],PrimeQ[IntegerReverse[Times@@#]]&][[;;,1]] (* Harvey P. Dale, Feb 10 2024 *)
Showing 1-4 of 4 results.

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

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