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.

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A089268 Odd semiprimes m such that m-2 is composite.

Original entry on oeis.org

35, 51, 57, 65, 77, 87, 93, 95, 119, 121, 123, 143, 145, 155, 161, 177, 185, 187, 203, 205, 209, 215, 217, 219, 221, 237, 247, 249, 267, 287, 289, 291, 299, 301, 303, 305, 321, 323, 327, 329, 335, 341, 365, 371, 377, 393, 395, 407, 413, 415, 417, 427, 437
Offset: 1

Views

Author

Reinhard Zumkeller, Oct 28 2003

Keywords

Comments

A087942(a(n)) = 0.
Assuming Goldbach's conjecture that every even number greater than 2 is the sum of two primes, these are the numbers that are the product of two primes but not the sum of two primes. - Michael B. Porter, Feb 08 2013

Links

Crossrefs

Cf. A062721, A046315, A001358.

Programs

  • Mathematica
    Take[Select[Union[Flatten[Table[Prime[i] Prime[j], {i, 2, 25}, {j, 2, 25}]]], Not[PrimeQ[# - 2]] &], 50] (* Alonso del Arte, Feb 08 2013 *)
  • PARI
    isok(m) = (m%2) && (bigomega(m)==2) && !isprime(m-2); \\ Michel Marcus, Oct 19 2021
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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