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.

A096821 Solutions to Mod[sigma(x),x]=12 of the form p*(p+13)/2 where p is a prime of form=2^j-13, of which j exponents are listed in A096818.

Original entry on oeis.org

24, 304, 127744, 33501184, 8589082624, 10384593717069654320312270165377024, 822752278660603021077484591278411581166520461101278617407586304, 15177100720513508366558296147058741458142670970377727126573378340391656803557965824
Offset: 1

Views

Author

Labos Elemer, Jul 13 2004

Keywords

Comments

The relevant A084306 includes additional solution like 21, while A076496 contains solutions of 6k form too.

Examples

			8th term is (2^136)*(-13+2^137) with 83 decimal digits; n=4: a[4]=(2^3)*(16-13)=24;

Links

Crossrefs

Cf. A084306, A096518, A000203, A076496.

A216697 Numbers n such that sigma(n) mod n = 12, n is divisible by 6, but n/6 is not prime.

Original entry on oeis.org

24, 54, 780, 2352, 430272, 184773312
Offset: 1

Views

Author

Michel Marcus, Sep 15 2012

Keywords

Comments

Motivated by A076496 comment: if n=6p, p>3 prime, then Mod(sigma(n),n)=12. So this sequence is included in A076496, but not in A084306.
Next term > 10^11. - Donovan Johnson, Sep 27 2012

Examples

			sigma(24) = 60 = 2*24+12, but 24/6=4 is not prime.

Crossrefs

Cf. A076496, A084306.

Programs

  • PARI
    isOk(n) = { return ((n % 6 == 0) && (! isprime(n/6)) && (sigma(n) % n == 12));}

A234238 Sporadic solutions to sigma(n) == 12 modulo n.

Original entry on oeis.org

24, 54, 121, 304, 780, 2352, 127744, 430272, 33501184, 184773312, 8589082624
Offset: 1

Views

Author

Michel Marcus, Dec 21 2013

Keywords

Comments

Terms of A076496 that are either not divisible by 6 or such that x/6 is not coprime to 6.
10384593717069654320312270165377024 is also a term. - Donovan Johnson, Dec 23 2013

Examples

			sigma(24) % 24 = 12, and 24/6 is not coprime to 6, hence 24 is here.
sigma(121) % 121 = 12, and 121 is not divisible by 6, hence 121 is here.

Links

Crossrefs

Cf. A076496.
Supersequence of A084306.

Programs

  • PARI
    a(n) = m = 6; a = sigma(m) ; ((sigma(n) % n) == a) && ((n % m) || (!(n % m) && (gcd(m, (n/m)) != 1)));

Extensions

a(11) from Donovan Johnson, Dec 23 2013
Showing 1-3 of 3 results.

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