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 1-6 of 6 results.

A171256 Numbers n such that sigma(n) = 10*phi(n) (where sigma=A000203, phi=A000010).

Original entry on oeis.org

168, 270, 570, 2376, 2436, 5016, 6426, 7110, 13566, 15834, 34452, 58520, 62568, 72732, 75210, 113832, 126882, 168756, 169218, 191862, 199368, 223938, 240312, 280488, 308568, 321468, 420888, 449442, 472758, 661848, 673608, 776736, 848540, 854496, 907236
Offset: 1

Views

Author

M. F. Hasler, Mar 19 2010

Keywords

Comments

If n is in this sequence, then for any prime p not dividing n, sigma(np) - 10*phi(np) = 2*sigma(n).

Links

Crossrefs

Cf. A062699, A068391, A074400, A068390, A136547, A104900, A136540, A104901, A163667, A171257, A104902, A171258, A171259, A171260, A104903.

Programs

  • Mathematica
    Select[Range[10^6], DivisorSigma[1, #] == 10 * EulerPhi[#] &] (* Amiram Eldar, Dec 04 2019 *)
  • PARI
    for(k=1,10^6, sigma(k) - 10*eulerphi(k) || print1(k", "));

A171257 Numbers n such that sigma(n) = 11*phi(n) (where sigma=A000203, phi=A000010).

Original entry on oeis.org

2580, 16770, 18630, 28896, 35970, 61404, 66024, 147576, 163944, 215124, 224010, 296184, 399126, 408672, 443394, 464340, 476010, 574308, 856086, 862752, 868428, 931224, 957348, 1004910, 1110186, 1496610, 1721720, 1723290, 1833348, 1971288, 2139852, 2234790
Offset: 1

Views

Author

Farideh Firoozbakht and M. F. Hasler, Mar 19 2010

Keywords

Links

Crossrefs

Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A104902, A171258, A171259, A171260, A104903.

Programs

  • Mathematica
    Select[Range[10^6], DivisorSigma[1, #] == 11 * EulerPhi[#] &] (* Amiram Eldar, Dec 04 2019 *)
  • PARI
    for(k=1,2e6, sigma(k) - 11*eulerphi(k) || print1(k", "));

A171258 Numbers n such that sigma(n) = 13*phi(n) (where sigma=A000203, phi=A000010).

Original entry on oeis.org

630, 5544, 11160, 18810, 27000, 57000, 80388, 161820, 178020, 182880, 242820, 265608, 388620, 391500, 447678, 465192, 522522, 671760, 690120, 711000, 775170, 826500, 901170, 1051830, 1102290, 1157130, 1418160, 1578330, 1679400, 1812384, 1874520, 1993824
Offset: 1

Views

Author

Farideh Firoozbakht and M. F. Hasler, Mar 19 2010

Keywords

Links

Crossrefs

Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A171257, A104902, A171259, A171260, A104903.

Programs

  • Mathematica
    Select[Range[2*10^6],DivisorSigma[1,#]==13EulerPhi[#]&] (* Harvey P. Dale, Mar 29 2018 *)
  • PARI
    for(k=1,2e6, sigma(k) - 13*eulerphi(k) || print1(k", "));

A171259 Numbers n such that sigma(n) = 14*phi(n) (where sigma=A000203, phi=A000010).

Original entry on oeis.org

420, 2730, 5940, 12540, 24024, 38610, 48360, 66528, 77490, 81510, 133920, 140448, 141372, 156420, 163590, 282720, 284580, 298452, 348348, 498420, 600780, 681912, 701220, 771420, 792480, 901530, 918918, 1016730, 1052220, 1150968, 1372680, 1439592, 1654620
Offset: 1

Views

Author

Farideh Firoozbakht and M. F. Hasler, Mar 19 2010

Keywords

Links

Crossrefs

Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A171257, A104902, A171258, A171260, A104903.

Programs

  • Mathematica
    Select[Range[10^6], DivisorSigma[1, #] == 14 * EulerPhi[#] &] (* Amiram Eldar, Dec 04 2019 *)
  • PARI
    for(k=1,2e6, sigma(k) - 14*eulerphi(k) || print1(k", "));

A171260 Numbers n such that sigma(n) = 15*phi(n) (where sigma=A000203, phi=A000010).

Original entry on oeis.org

840, 11880, 12180, 25080, 32130, 67830, 79170, 172260, 282744, 312840, 363660, 569160, 596904, 634410, 696696, 843780, 846090, 959310, 996840, 1119690, 1201560, 1402440, 1542840, 1607340, 1929312, 2104440, 2247210, 2363790, 3309240, 3368040, 3883680
Offset: 1

Views

Author

Farideh Firoozbakht and M. F. Hasler, Mar 19 2010

Keywords

Links

Crossrefs

Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A171257, A104902, A171258, A171259, A104903.

Programs

  • Mathematica
    Select[Range[10^6], DivisorSigma[1, #] == 15 * EulerPhi[#] &] (* Amiram Eldar, Dec 04 2019 *)
  • PARI
    for(k=1,3e6, sigma(k) - 15*eulerphi(k) || print1(k", "));

A110598 Balanced numbers k such that k mod 12 = 5.

Original entry on oeis.org

137885, 145145, 3501605, 6605945, 6953765, 8409305, 10055045, 11413205, 11569805, 16540205, 18545285, 19648805, 21902705, 22806905, 25965005, 26655005, 29811665, 45680921, 71569745, 79989845, 91681289, 196492205, 214218389, 223086125, 229554941, 233601641
Offset: 1

Views

Author

Walter Kehowski, Sep 13 2005

Keywords

Comments

For the first 26 terms, the quotient sigma(k)/phi(k) is 2 or 3.

Links

Crossrefs

Intersection of A017581 and A020492.
Cf. A000010, A000203, A062699, A068391.

Programs

  • Maple
    with(numtheory); BNM5:=[]: for z from 1 to 1 do for m from 1 to 1000000 do n:=12*m+5; if sigma(n) mod phi(n) = 0 then BNM5:=[op(BNM5),n] fi; od; od; BNM5;
  • Mathematica
    Select[Range[5,12000000,12],MemberQ[{2,3},DivisorSigma[1,#]/EulerPhi[#]]&]  (* Harvey P. Dale, May 06 2012 *)

Extensions

a(10)-a(26) from Donovan Johnson, Aug 30 2012
Showing 1-6 of 6 results.

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