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.

A358931 a(n) is the smallest n-gonal pyramidal number with binary weight n.

Original entry on oeis.org

35, 30, 405, 95, 6860, 765, 28855, 7923, 96760, 380091, 259064, 915915, 3845501, 1436415, 32471830, 11992255, 62904941, 182171613, 266182382, 670936891, 939382515, 2533347310, 30530860911, 1876688877, 16972115903, 201845686175, 529756691451, 409027868651, 2713039388125
Offset: 3

Views

Author

Ilya Gutkovskiy, Dec 06 2022

Keywords

Examples

			405 is the smallest pentagonal pyramidal number with binary weight 5 (405_10 = 110010101_2), so a(5) = 405.

Links

Crossrefs

Cf. A000120, A358930, A358932.

Programs

  • Mathematica
    p[n_, k_] := k*(k + 1)*((n - 2)*k + 5 - n)/6; a[n_] := Module[{k = 1, pk}, While[DigitCount[pk = p[n, k], 2, 1] != n, k++]; pk]; Array[a, 30, 3] (* Amiram Eldar, Dec 09 2022 *)

A358932 a(n) is the smallest centered n-gonal number with binary weight n.

Original entry on oeis.org

19, 85, 31, 469, 253, 2025, 5995, 4061, 15742, 48061, 8191, 220543, 384766, 3080161, 3272671, 6192631, 8385271, 31453021, 58159102, 249495467, 401469279, 268418041, 134193151, 2885548927, 1610563582, 8589393821, 33280753395, 83751780091, 171658174447
Offset: 3

Views

Author

Ilya Gutkovskiy, Dec 06 2022

Keywords

Examples

			31 is the smallest centered pentagonal number with binary weight 5 (31_10 = 11111_2), so a(5) = 31.

Links

Crossrefs

Cf. A000120, A358930, A358931.

Programs

  • Mathematica
    c[n_, k_] := n*k*(k + 1)/2 + 1; a[n_] := Module[{k = 1, ck}, While[DigitCount[ck = c[n, k], 2, 1] != n, k++]; ck]; Array[a, 25, 3] (* Amiram Eldar, Dec 09 2022 *)

A359003 a(n) is the smallest n-gonal number whose sum of digits is n.

Original entry on oeis.org

3, 4, 5, 6, 7, 8, 9, 370, 506, 156, 238, 671, 726, 88, 836, 585, 775, 7337, 5268, 8149, 8555, 8961, 9367, 9773, 15786, 9856, 91964, 65757, 89428, 179960, 47796, 108979, 197945, 86976, 467974, 998516, 259896, 598792, 1737788, 869649, 969991, 1985984, 998676, 3798496, 7979546, 5877696
Offset: 3

Views

Author

Ilya Gutkovskiy, Dec 10 2022

Keywords

Examples

			370 is the smallest 10-gonal number with digit sum 10, so a(10) = 370.

Links

Crossrefs

Cf. A007953, A051885, A062685, A062688, A358930.

Programs

  • Mathematica
    p[n_, k_] := (n - 2)*k*(k - 1)/2 + k; a[n_] := Module[{k = 1, pk}, While[Plus @@ IntegerDigits[pk = p[n, k]] != n, k++]; pk]; Array[a, 45, 3] (* Amiram Eldar, Dec 10 2022 *)
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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