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 1-3 of 3 results.

A231407 Positive integers that are not the sum of distinct primes.

Original entry on oeis.org

1, 4, 6
Offset: 1

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Author

Jonathan Sondow, Nov 24 2013

Keywords

Comments

Using elementary methods, Richert proved that 6 is the largest integer which is not the sum of distinct primes.

References

  • H.-E. Richert, Über Zerlegungen in paarweise verschiedene Zahlen, Norsk. Mat. Tidsskr., 31 (1949), 120-122.

Crossrefs

Formula

a(3) = A121571(1).

A234320 Largest number that is not the sum of distinct primes of the form 2k+1, 4k+1, 4k+3, 6k+1, 6k+5, ...; or 0 if none exists.

Original entry on oeis.org

9, 121, 55, 205, 161
Offset: 1

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Author

Jonathan Sondow, Dec 28 2013

Keywords

Comments

Largest number that is not the sum of distinct primes of the form 2nk+r for fixed n > 0 and 0 < r < 2n with gcd(2n,r) = 1.
n = 1: Dressler proved that 9 is the largest integer which is not the sum of distinct odd primes.
n = 2 and 3: Makowski proved that the largest integer that is not the sum of distinct primes of the form 4k+1, 4k+3, 6k+1, 6k+5 is 121, 55, 205, 161, respectively.
n = 6: Dressler, Makowski, and Parker proved that the largest integer that is not the sum of distinct primes of the form 12k+1, 12k+5, 12k+7, 12k+11 is 1969, 1349, 1387, 1475.
For n = 4, 5, 7, 8, 9, ..., the largest number that is not the sum of distinct primes of the form 2nk+r seems to be unknown.

Examples

			The positive integers that are not the sum of distinct odd primes are A231408 = 1, 2, 4, 6, 9, so a(1) = A231408(5) = 9.
		

References

  • A. Makowski, Partitions into unequal primes, Bull. Acad. Polon. Sci. Sér. Math. Astronom. Phys., 8 (1960), 125-126.

Crossrefs

A234321 Positive integers that are not the sum of distinct Ramanujan primes.

Original entry on oeis.org

1, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 23, 24, 25, 26, 27, 32, 33, 34, 35, 36, 37, 38, 39, 44, 45, 50, 51, 53, 55, 56, 62, 63, 65, 68, 74, 79, 85, 91, 92, 94, 122
Offset: 1

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Author

Jonathan Sondow, Dec 28 2013

Keywords

Comments

Paksoy showed that every integer > 122 is the sum of distinct Ramanujan primes (A104272).

Crossrefs

Showing 1-3 of 3 results.