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.

A364258 a(n) = A163511(n) - n.

Original entry on oeis.org

1, 1, 2, 0, 4, 4, 0, -2, 8, 18, 8, 14, 0, 2, -4, -8, 16, 64, 36, 106, 16, 54, 28, 26, 0, 20, 4, 8, -8, -8, -16, -20, 32, 210, 128, 590, 72, 338, 212, 304, 32, 184, 108, 202, 56, 102, 52, 74, 0, 86, 40, 124, 8, 52, 16, 22, -16, 6, -16, -4, -32, -28, -40, -50, 64, 664, 420, 3058, 256, 1806, 1180, 2330, 144, 1052, 676
Offset: 0

Views

Author

Antti Karttunen, Jul 25 2023

Keywords

Comments

Compare also to the scatter plot of A364294.

Crossrefs

Cf. A007283, A163511, A364255 [= gcd(n,a(n))], A364287 (positions of negative terms), A364292 (of terms <= 0), A364288, A364294 [= -a(A364293(n))].

Programs

  • Mathematica
    f[n_] := Reverse@ Map[Ceiling[(Length@ # - 1)/2] &, DeleteCases[Split@ Join[Riffle[IntegerDigits[n, 2], 0], {0}], {k__} /; k == 1]]; {1}~Join~Table[-n + Function[t, Prime[t] Product[Prime[m]^(f[n][[m]]), {m, t}] ][DigitCount[n, 2, 1]], {n, 120}] (* Michael De Vlieger, Jul 25 2023 *)
  • Python
    from sympy import nextprime
    def A364258(n):
        c, p, k = 1, 1, n
        while k:
            c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
            k >>= s+1
        return c*p-n # Chai Wah Wu, Jul 25 2023

Formula

a(n) = A364288(A163511(n)).
For n >= 1, a(2*n) = 2*a(n).
For n >= 0, a(A007283(n)) = 0.

A364293 Odd numbers k for which A163511(k) <= k.

Original entry on oeis.org

3, 7, 15, 29, 31, 59, 61, 63, 119, 121, 123, 125, 127, 223, 239, 245, 247, 249, 251, 253, 255, 383, 447, 479, 493, 495, 497, 499, 501, 503, 505, 507, 509, 511, 767, 895, 957, 959, 989, 991, 999, 1001, 1003, 1005, 1007, 1009, 1011, 1013, 1015, 1017, 1019, 1021, 1023, 1535, 1789, 1791, 1917, 1919, 1977, 1979, 1981
Offset: 1

Views

Author

Antti Karttunen, Jul 25 2023

Keywords

Crossrefs

Odd terms in A364292.
Cf. A000225 (subsequence apart from its two initial terms), A163511, A364294 [= -A364258(a(n))].

A364563 Difference k - A005940(k) computed for those odd numbers k for which the difference is nonnegative.

Original entry on oeis.org

0, 0, 0, 2, 6, 20, 2, 48, 28, 4, 110, 80, 48, 18, 18, 234, 202, 166, 110, 132, 12, 64, 42, 24, 484, 446, 402, 348, 360, 238, 50, 68, 276, 132, 246, 186, 204, 240, 994, 940, 884, 824, 830, 690, 462, 526, 722, 560, 240, 192, 680, 300, 596, 194, 602, 614, 696, 2012, 1958, 1898, 1794, 1840, 1624, 1336, 1442, 1724, 1458
Offset: 1

Views

Author

Antti Karttunen, Aug 06 2023

Keywords

Crossrefs

Cf. also A364294.

Formula

a(n) = -A364499(A364543(n)).
Showing 1-3 of 3 results.