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.

A344466 Primes that occur as p + (digit product of p) for p in A092518.

Original entry on oeis.org

29, 47, 67, 107, 109, 181, 251, 293, 331, 347, 431, 443, 457, 491, 547, 593, 631, 653, 659, 673, 743, 823, 827, 839, 929, 971, 977, 1091, 1129, 1181, 1231, 1237, 1279, 1321, 1327, 1423, 1433, 1447, 1471, 1483, 1493, 1499, 1553, 1559, 1579, 1601, 1777, 1823, 1867, 1871, 1951, 1993, 2113, 2137
Offset: 1

Views

Author

J. M. Bergot and Robert Israel, May 20 2021

Keywords

Comments

Terms are unique and in numerical order.
There are terms that correspond to more than one member of A092518, such as 827 = 683+6*8*3 = 743+7*4*3.

Examples

			a(4) = 107 is a term because 83 = A092518(5) and 107 = 83+8*3.
		

Crossrefs

Programs

  • Maple
    N:= 10000: # to get terms <= N
    S:= {}:
    p:= 1:
    do
      p:= nextprime(p);
      if p >= N then break fi;
      L:= convert(p,base,10);
      if member(0,L) then next fi;
      q:= p + convert(L,`*`);
      if q <= N and isprime(q) then
         S:= S union {q};
      fi
    od:
    sort(convert(S,list));

A157677 Primes p such that p + (product of digits of p) is also prime.

Original entry on oeis.org

23, 29, 61, 67, 83, 101, 103, 107, 109, 163, 233, 239, 283, 293, 307, 347, 349, 401, 409, 431, 439, 443, 449, 499, 503, 509, 563, 569, 601, 607, 613, 617, 619, 653, 659, 677, 683, 701, 709, 743, 809, 907, 929, 941, 1009, 1013, 1019, 1021, 1031, 1033, 1039
Offset: 1

Views

Author

Kyle D. Balliet, Mar 04 2009

Keywords

Comments

If p contains a zero, then p is trivially a member.

Examples

			83 is prime, and 83 + 8*3 = 89 which is also prime. 103 is prime, and 103 + 1*0*3 = 103 is also prime. Thus 89 and 103 are members.
		

Crossrefs

Union of A092518 and A056709.
Cf. A225303.

Programs

  • Maple
    a := proc (n) local nn: nn := convert(ithprime(n), base, 10): if isprime(ithprime(n)+product(nn[j], j = 1 .. nops(nn))) = true then ithprime(n) else end if end proc: seq(a(n), n = 1 .. 180); # Emeric Deutsch, Mar 08 2009
  • Mathematica
    Select[Prime[Range[175]], PrimeQ[# + Times @@ IntegerDigits[#]] &] (* Jayanta Basu, Apr 22 2013 *)
  • PARI
    dprod(n)=n=digits(n); prod(i=1,#n,n[i])
    is(n)=isprime(n) && isprime(n+dprod(n)) \\ Charles R Greathouse IV, Dec 27 2013

Formula

a(n) ~ n log n. - Charles R Greathouse IV, Apr 22 2013

Extensions

More terms from Emeric Deutsch, Mar 08 2009

A157676 Numbers n such that n + (product of digits of n) is prime.

Original entry on oeis.org

1, 21, 23, 27, 29, 61, 67, 81, 83, 101, 103, 107, 109, 161, 163, 169, 233, 239, 253, 259, 283, 289, 293, 299, 307, 329, 341, 343, 347, 349, 361, 401, 409, 431, 437, 439, 441, 443, 449, 471, 473, 477, 493, 499, 503, 509, 529, 563, 569, 601, 607, 611, 613, 617
Offset: 1

Views

Author

Kyle D. Balliet, Mar 04 2009

Keywords

Examples

			a(21) = 21 + (2)(1) = 23 (prime). a(67) = 67 + (6)(7) = 109 (prime). a(169) = 169 + (1)(6)(9) = 223 (prime).
		

Crossrefs

Programs

  • Mathematica
    fQ[n_] := PrimeQ[n + Times @@ IntegerDigits@n]; Select[ Range@1000, fQ@# &] (* Robert G. Wilson v, May 04 2009 *)
  • PARI
    dprod(n)=n=digits(n);prod(i=1,#n,n[i])
    is(n)=isprime(dprod(n)+n) \\ Charles R Greathouse IV, Dec 27 2013

Formula

a(n) ~ n log n. - Charles R Greathouse IV, Dec 27 2013

Extensions

More terms from Robert G. Wilson v, May 04 2009

A092529 Primes p such that both the digit sum of p plus p and the digit product of p plus p are also primes.

Original entry on oeis.org

163, 233, 293, 431, 499, 563, 617, 743, 1423, 1483, 1489, 1867, 2273, 2543, 2633, 3449, 4211, 4217, 4273, 4547, 4729, 5861, 6121, 6529, 6637, 6653, 6761, 6857, 6949, 7681, 8273, 8431, 8837, 8839, 9649, 9689
Offset: 1

Views

Author

Ray G. Opao, Apr 08 2004

Keywords

Comments

Intersection of A048519 and A092518.
Zeros are not permitted in p; thus, for example, 101 is not included. - Harvey P. Dale, May 25 2013

Examples

			a(2) = 233: 233+(2+3+3) = 233+8 = 241, which is prime. 233+(2*3*3) = 233+18 = 251, which is prime.
		

Crossrefs

Programs

  • Maple
    filter:= proc(p) local L;
      if not isprime(p) then return false fi;
      L:= convert(p,base,10);
      if member(0,L) then return false fi;
      isprime(p + convert(L,`+`)) and isprime(p + convert(L,`*`))
    end proc:
    select(filter, [seq(i,i=3..10000,2)]); # Robert Israel, Feb 20 2024
  • Mathematica
    pppQ[n_]:=Module[{idn=IntegerDigits[n]},!MemberQ[idn,0]&&And@@PrimeQ[ {n+ Total[idn], n+Times@@idn}]]; Select[Prime[Range[1200]],pppQ] (* Harvey P. Dale, May 25 2013 *)

Extensions

More terms from Robert G. Wilson v, Apr 10 2004
Showing 1-4 of 4 results.