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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A291620 Branch term s_n(b), b > 1 of equivalence classes of prime sequences {s_n(k)} for k > 0 derived by records of first differences of Rowland-like recurrences with increasing even start values >= 4.

Original entry on oeis.org

0, 0, 0, 0, 131, 0, 233, 167, 2381, 647, 0, 233, 0, 941, 263, 0, 0, 353, 0, 0, 797, 0, 0, 0, 941, 0, 0, 8273, 569, 0, 0, 569, 1181, 0, 0, 22133, 761, 0, 761, 1721, 839, 1811, 881, 0, 1811, 929, 1973, 0, 0, 1049, 1181, 9323, 2309, 1187, 0, 2441, 2441
Offset: 1

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Author

Ralf Steiner, Aug 28 2017

Keywords

Comments

See A291528 (leaves) for equivalence classes.
If the conjecture of an inverse tree of primes with the leaves in A291528 using the same index n holds, except a(1)=0 all terms a(n) == 0 indicates that the branch point is not yet found.
This is a k-ary tree, k > 2, such as a(7) == a(12) == 233.
Maybe these simple Rowland-like recurrences giving all primes are related to a simple bounded physical quantum system with a "Hamiltonian for the zeros of the Riemann zeta function" (cf. Bender et al.) having degenerated energy eigenvalues a(n).
[Note: the editors feel that any such connection is extremely unlikely. - N. J. A. Sloane, Oct 30 2017]

Examples

			n=5: Some equivalence classes of prime sequences {s_n(k)} have the same tail for a constant C_n < k, such as {s_2(k)} = {7,13,29,59,131,...} and {s_5(k)} = {31,61,131,...} with common tail {a(5),...} = {131,...} and the branch 131 = a(5). Thus it seems that all terms != 0 are branches of a kind of an inverse prime-tree with the root at infinity.
		

Crossrefs

Cf. A134162, A134734, A167168 (equivalence classes), A291528 (leaves)

Programs

  • Mathematica
    For[i = 2; pl = {}; fp = {}; bp = {}, i < 350, i++,
    ps = Union@FoldList[Max, 1, Rest@# - Most@#] &@
       FoldList[#1 + GCD[#2, #1] &, 2 i, Range[2, 10^5]];
    p = Select[ps, (i <= #) && ! MemberQ[pl, #] &, 1];
    If[p != {},
      fp = Join[fp, {p}];
      b = Select[Drop[ps, po = Position[ps, p[[1]]][[1]][[1]]],
        MemberQ[pl, #] &, 1];
      If[b != {}, bp = Join[bp, {b}], bp = Join[bp, {{0}}]];
      pl = Union[pl, Drop[ps, po - 1]]]]; Flatten@bp

Formula

a(n) > A291528(n) || a(n) == 0.
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