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 1-4 of 4 results.

A036921 Numbers n such that digit sum of n equals digit sum of 'juxtaposition' and 'sum' of its prime factors (counted with multiplicity).

Original entry on oeis.org

4, 22, 27, 94, 121, 166, 202, 265, 274, 346, 355, 382, 438, 454, 517, 526, 562, 634, 706, 852, 913, 915, 922, 1086, 1111, 1165, 1219, 1255, 1282, 1507, 1626, 1633, 1642, 1822, 1894, 1903, 1966, 2067, 2155, 2173, 2182, 2227, 2265, 2326, 2362, 2409, 2434
Offset: 1

Views

Author

Patrick De Geest, Jan 04 1999

Keywords

Crossrefs

Cf. A006753, A036920, A019506.

Programs

  • Mathematica
    d[n_]:=IntegerDigits[n]; co[n_,k_]:=Nest[Flatten[d[{#,n}]]&,n,k-1]; t={}; Do[If[!PrimeQ[n]&&Total[d[n]]==Total[d[Total[Times@@@(x=FactorInteger[n])]]]==Total[Flatten[d[co@@@x]]],AppendTo[t,n]],{n,4,2435}]; t (* Jayanta Basu, Jun 04 2013 *)

A230357 Numbers n such that digit sum of n equals digit sum of sopf(n) (sum of the distinct prime factors of n).

Original entry on oeis.org

22, 94, 105, 114, 136, 140, 160, 166, 202, 222, 234, 250, 265, 274, 346, 355, 361, 382, 424, 438, 445, 454, 516, 517, 526, 532, 562, 634, 702, 706, 712, 732, 812, 913, 915, 922, 1036, 1071, 1086, 1111, 1116, 1122, 1138, 1165, 1185, 1204, 1206, 1219, 1221, 1230, 1239, 1255, 1282, 1312, 1316, 1318, 1345, 1363, 1400, 1404, 1432, 1507, 1520, 1530, 1550
Offset: 1

Views

Author

Antonio Roldán, Oct 16 2013

Keywords

Examples

			166=2*83. Sopf(166)=85. Digit_sum(166)=13, digit_sum(85)=13.

Crossrefs

Cf. A006753, A036920, A230354, A230355, A230356.

Programs

  • PARI
    sopf(n)= { local(f, s=0); f=factor(n); for(i=1, matsize(f)[1], s+=f[i, 1]); return(s) }
digsum(n)={local (d, p); d=0; p=n; while(p, d+=p%10; p=floor(p/10)); return(d)}
{for (n=4, 2*10^3,m=sopf(n);if(digsum(n)==digsum(m)&&m<>n,print(n)))}

A036922 Even composite numbers whose digit sum equals the digit sum of (sum of prime factors, counted with multiplicity).

Original entry on oeis.org

4, 22, 94, 114, 150, 166, 202, 204, 222, 224, 274, 342, 346, 382, 438, 450, 454, 526, 540, 562, 612, 634, 640, 706, 852, 922, 1068, 1086, 1120, 1122, 1138, 1200, 1230, 1232, 1282, 1314, 1318, 1400, 1626, 1642, 1770, 1820, 1822, 1894, 1966, 2070, 2080
Offset: 1

Views

Author

Patrick De Geest, Jan 04 1999

Keywords

Crossrefs

Cf. A006753, A036920, A019506.

Programs

  • PARI
    isok(n)=my(f=factor(n)); n%2==0 && n>2 && sumdigits(sum(i=1, #f~, f[i,1]*f[i,2])) == sumdigits(n) \\ Andrew Howroyd, Jun 19 2021

Extensions

Title reworded by Sean A. Irvine, Nov 30 2020

A036923 Odd composite numbers n such that the digit sum of n equals digit sum of sum of its prime factors (counted with multiplicity).

Original entry on oeis.org

27, 105, 121, 265, 315, 355, 445, 517, 841, 913, 915, 1111, 1165, 1185, 1219, 1221, 1239, 1255, 1345, 1363, 1507, 1633, 1903, 2067, 2101, 2155, 2173, 2209, 2227, 2245, 2265, 2335, 2409, 2515, 2533, 2605, 2965, 3091, 3129, 3219, 3235, 3417, 3505, 3507
Offset: 1

Views

Author

Patrick De Geest, Jan 04 1999

Keywords

Crossrefs

Cf. A006753, A036920, A019506.

Programs

  • Mathematica
    ds[n_]:=Total[IntegerDigits[n]]; t={}; Do[If[!PrimeQ[n]&&ds[n]==ds[Total[ Times@@@FactorInteger[n]]],AppendTo[t,n]],{n,9,3508,2}]; t (* Jayanta Basu, Jun 04 2013 *)

Extensions

Title reworded by Sean A. Irvine, Nov 30 2020
Showing 1-4 of 4 results.

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

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