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.

A290224 Numbers n such that A290223(n) = 0.

Original entry on oeis.org

1, 19, 81, 162, 181, 199, 243, 262, 324, 343, 405, 424, 486, 505, 567, 648, 685, 729, 766, 810, 847, 891, 910, 928, 972, 1053, 1072, 1134, 1153, 1215, 1234, 1296, 1315, 1377, 1458, 1495, 1539, 1576, 1620, 1657, 1701, 1720, 1738, 1782, 1801, 1819, 1863, 1944, 1981, 1999, 2025, 2044, 2106, 2125, 2187, 2206, 2268
Offset: 1

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Author

Derek Orr, Jul 24 2017

Keywords

Comments

This sequence is believed to be infinite.

Examples

			181 is in this sequence because 181 - (1+8+1)^2 = 81. Then 81 - (8+1)^2 = 0.

Crossrefs

Cf. A007953, A003132, A290223.

Programs

  • PARI
    a(n)=k=n; c=1; v=List(); listput(v, k); while(c, if(k>=0, k-=sumdigits(k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); if(k<0, k+=sumdigits(-k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); c+=1)
for(n=1,10^4,if(a(n)==0,print1(n,", ")))

A290226 Numbers n such that A290223(n) = 2.

Original entry on oeis.org

2, 23, 62, 77, 119, 194, 287, 398
Offset: 1

Views

Author

Derek Orr, Jul 24 2017

Keywords

Comments

This sequence is believed to be finite. a(9) > 10^5, if it exists.

Examples

			62 is in this sequence because 62 - (6+2)^2 = -2. Then -2 + (2)^2 = 2.

Crossrefs

Cf. A007953, A003132, A290223.

Programs

  • PARI
    a(n)=k=n; c=1; v=List(); listput(v, k); while(c, if(k>=0, k-=sumdigits(k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); if(k<0, k+=sumdigits(-k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); c+=1)
for(n=1,10^5,if(a(n)==2,print1(n,", ")))

A290227 Numbers n such that A290223(n) = 11.

Original entry on oeis.org

8, 17, 26, 29, 35, 38, 47, 56, 65, 74, 83, 92, 149, 158, 167, 197
Offset: 1

Views

Author

Derek Orr, Jul 24 2017

Keywords

Comments

This sequence is believed to be finite. If it exists, a(17) > 10^5.

Examples

			26 is in this sequence because 26 - (2+6)^2 = -38. Then -38 + (3+8)^2 = 83. Then 83 - (8+3)^2 = -38, and so on.

Crossrefs

Cf. A007953, A003132, A290223.

Programs

  • PARI
    a(n)=k=n; c=1; v=List(); listput(v, k); while(c, if(k>=0, k-=sumdigits(k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); if(k<0, k+=sumdigits(-k)^2; c+=1; if(k==2||k==3||k==0||k==6||k==9, return(k)); if(vecsearch(Vec(v), k), return(sumdigits(abs(k)))); listput(v, k)); c+=1)
for(n=1,10^5,if(a(n)==11,print1(n,", ")))
Showing 1-3 of 3 results.

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

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