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.

A363245 Lexicographically first sequence of positive integers such that all terms are pairwise coprime and no subset sum is a power of 2.

Original entry on oeis.org

3, 7, 10, 11, 17, 31, 41, 71, 169, 199, 263, 337, 367, 1553, 2129, 2287, 2297, 4351, 10433, 16391, 16433, 34829, 65543, 69557, 165887, 262151, 358481, 817153, 952319, 1048583, 3704737, 3932167, 4518071, 12582919, 17305417, 17367019, 50069497, 50593799, 87228517
Offset: 1

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Crossrefs

Cf. A353889.

Programs

  • Mathematica
    a = {3}; k = 2; Monitor[Do[While[Or[! Apply[CoprimeQ, Join[a, {k}]], AnyTrue[Map[Log2 @* Total@ Append[#, k] &, Subsets[a]], IntegerQ]], k++]; AppendTo[a, k]; k++, {i, 16}], {i, k}]; a (* Michael De Vlieger, Jun 14 2023 *)
  • Python
    from math import gcd
    from itertools import count, islice
    def agen(): # generator of terms
        a, ss, pows2, m = [], set(), {1, 2}, 2
        for k in count(1):
            if k in pows2: continue
            elif k > m: m <<= 1; pows2.add(m)
            if any(p2-k in ss for p2 in pows2): continue
            if any(gcd(ai, k) != 1 for ai in a): continue
            a.append(k); yield k
            ss |= {k} | {k+si for si in ss if k+si not in ss}
            while m < max(ss): m <<= 1; pows2.add(m)
    print(list(islice(agen(), 30))) # Michael S. Branicky, Jun 09 2023

Extensions

a(23)-a(33) from Michael S. Branicky, Jun 07 2023
a(34)-a(39) from Jon E. Schoenfield, Jun 09 2023