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.

A235690 Semiprimes which have one or more occurrences of exactly two different digits.

Original entry on oeis.org

10, 14, 15, 21, 25, 26, 34, 35, 38, 39, 46, 49, 51, 57, 58, 62, 65, 69, 74, 82, 85, 86, 87, 91, 93, 94, 95, 115, 118, 119, 121, 122, 133, 141, 155, 161, 166, 177, 202, 221, 226, 262, 299, 303, 323, 334, 335, 339, 355, 377, 393, 411, 422, 445, 446, 447, 454
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Comments

The first term having a repeated digit is 115.

Examples

			1000000000010101 is a term because it is made of the digits 0 and 1 and it is the product of the two primes 18463559 and 54160739.

Crossrefs

Cf. A235691-A235696.
Cf. A235154-A235161.

Programs

  • Mathematica
    Select[Range[454], Length@Union@ IntegerDigits[#] == 2 && Total[Last /@ FactorInteger[#]] == 2 &] (* Giovanni Resta, Jan 14 2014 *)
  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(10000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==2, s=concat(s, b[n]))); s

A235691 Semiprimes which have one or more occurrences of exactly three different digits.

Original entry on oeis.org

106, 123, 129, 134, 142, 143, 145, 146, 158, 159, 169, 178, 183, 185, 187, 194, 201, 203, 205, 206, 209, 213, 214, 215, 217, 218, 219, 235, 237, 247, 249, 253, 254, 259, 265, 267, 274, 278, 287, 289, 291, 295, 298, 301, 302, 305, 309, 314, 319, 321, 326, 327
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Comments

The first term having a repeated digit is 1003.

Examples

			91119111691966691969 is a term, because it is made of the 3 digits {1, 6, 9} and is the product of two primes 9397848521 and 9695741689. - _Giovanni Resta_, Jan 14 2014

Crossrefs

Cf. A235690, A235692-A235696.
Cf. A235154-A235161.

Programs

  • Mathematica
    Select[Range@999, Length@ Union@ IntegerDigits[#] == 3 && Total[Last /@ FactorInteger[#]] == 2 &] (* Giovanni Resta, Jan 14 2014 *)
  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(10000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==3, s=concat(s, b[n]))); s

A235693 Semiprimes which have one or more occurrences of exactly five different digits.

Original entry on oeis.org

10237, 10238, 10239, 10249, 10265, 10279, 10294, 10297, 10327, 10342, 10345, 10347, 10349, 10358, 10367, 10378, 10379, 10389, 10394, 10397, 10423, 10435, 10462, 10473, 10483, 10489, 10493, 10495, 10497, 10523, 10537, 10543, 10546, 10547, 10562, 10573, 10579
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Comments

The first term having a repeated digit is 100235.
The first term that is a square is 12769. - Robert Israel, Jul 06 2018

Links

Crossrefs

Cf. A235690-A235692, A235694-A235696.
Cf. A235154-A235161.

Programs

  • Maple
    # to get all terms with 5 digits S:= combinat:-choose([$0..9],5):
f:= proc(x) local s,L;
      L:= convert(x,base,5);      if nops(L) < 5 then L:= [op(L),0$(5-nops(L))] fi;      if nops(convert(L,set))<5 then return NULL fi;
      op(select(t -> t > 10^4 and numtheory:-bigomega(t)=2, map(s -> add(s[L[i]+1]*10^(i-1),i=1..5),S)))
end proc:
sort(map(f, [$1..5^5-1])); # Robert Israel, Jul 06 2018
  • Mathematica
    Select[Range[10000,11000],PrimeOmega[#]==2&&Count[DigitCount[#],0]==5&] (* Harvey P. Dale, Apr 08 2015 *)
  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(15000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==5, s=concat(s, b[n]))); s

A235692 Semiprimes which have one or more occurrences of exactly four different digits.

Original entry on oeis.org

1027, 1037, 1042, 1043, 1046, 1047, 1057, 1059, 1067, 1073, 1079, 1082, 1094, 1203, 1205, 1207, 1234, 1238, 1243, 1247, 1253, 1257, 1263, 1267, 1273, 1285, 1286, 1293, 1294, 1306, 1329, 1345, 1346, 1347, 1349, 1354, 1357, 1369, 1379, 1382, 1385, 1387, 1389
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Comments

The first term having a repeated digit is 10027.

Crossrefs

Cf. A235690, A235691, A235693-A235696.
Cf. A235154-A235161.

Programs

  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(15000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==4, s=concat(s, b[n]))); s

A235694 Semiprimes which have one or more occurrences of exactly six different digits.

Original entry on oeis.org

102347, 102349, 102369, 102379, 102385, 102386, 102387, 102389, 102394, 102395, 102398, 102439, 102457, 102458, 102463, 102467, 102469, 102473, 102478, 102479, 102493, 102549, 102569, 102574, 102589, 102637, 102639, 102649, 102658, 102659, 102683, 102689
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Crossrefs

Cf. A235690-A235693, A235695, A235696.
Cf. A235154-A235161.

Programs

  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(103000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==6, s=concat(s, b[n]))); s

A235695 Semiprimes which have one or more occurrences of exactly seven different digits.

Original entry on oeis.org

1023469, 1023479, 1023547, 1023574, 1023586, 1023647, 1023649, 1023657, 1023689, 1023745, 1023746, 1023749, 1023794, 1023847, 1023879, 1023965, 1023985, 1024367, 1024369, 1024537, 1024538, 1024563, 1024567, 1024583, 1024637, 1024679, 1024687, 1024735
Offset: 1

Views

Author

Colin Barker, Jan 14 2014

Keywords

Crossrefs

Cf. A235690-A235694, A235696.
Cf. A235154-A235161.

Programs

  • PARI
    list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358
b=list(1030000); s=[]; for(n=1, #b, if(#vecsort(eval(Vec(Str(b[n]))),,8)==7, s=concat(s, b[n]))); s
Showing 1-6 of 6 results.

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