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.

Previous Showing 11-16 of 16 results.

A145825 a(n) is in A145818 such that (4n-1-a(n))/2 is in A145818 as well.

Original entry on oeis.org

1, 5, 1, 5, 17, 21, 17, 21, 1, 5, 1, 5, 17, 21, 17, 21, 65, 69, 65, 69, 81, 85, 81, 85, 65, 69, 65, 69
Offset: 1

Views

Author

Vladimir Shevelev, Oct 20 2008

Keywords

Comments

Note that a(4n)=a(4n-2), a(4n-1)=a(4n-3).

Crossrefs

A145818 A145812 A145819 A145822

A145866 Number of representations of 2n as a sum of two terms of A145819.

Original entry on oeis.org

1, 1, 2, 1, 2, 2, 2, 1, 2, 2, 3, 1, 2, 1, 1, 1, 2, 2, 3, 1, 3, 4, 3, 1, 2, 3, 2, 1, 1, 1, 1, 1, 2, 2, 3, 1, 3, 3, 2, 1, 3, 2, 5, 1, 3, 1, 1, 1, 2, 1
Offset: 1

Views

Author

Vladimir Shevelev, Oct 22 2008

Keywords

Crossrefs

A145819 A145812 A145818

A145869 a(n) is the least even positive integer which is not expressible as a sum A145819(s)+A145819(t), if both of s,t differ from n.

Original entry on oeis.org

2, 2, 4, 8, 30, 16, 28, 24, 114, 40, 58, 48, 100, 72, 92, 88
Offset: 1

Views

Author

Vladimir Shevelev, Oct 22 2008

Keywords

Crossrefs

A145819 A145812 A145818

A146091 a(n) = 3*A146085(n) - 2.

Original entry on oeis.org

1, 10, 19, 82, 91, 100, 163, 172, 181, 730, 739, 748, 811, 820, 829, 892, 901, 910, 1459, 1468, 1477, 1540, 1549, 1558, 1621, 1630, 1639, 6562, 6571, 6580, 6643, 6652, 6661, 6724, 6733, 6742, 7291, 7300, 7309, 7372, 7381, 7390, 7453, 7462, 7471, 8020, 8029, 8038, 8101, 8110, 8119
Offset: 1

Views

Author

Vladimir Shevelev, Oct 27 2008

Keywords

Comments

Positive integers such that for every integer m==4 (mod 9) there exists a unique representation of m as a sum of the form a(l)+3a(s).

Crossrefs

Cf. A146085, A146087, A145812, A145818.

Programs

  • PARI
    isa(n) = {my(d=Vecrev(digits(n, 3)), k=3); while (k <= #d, if (d[k], return (0)); k += 2;); d[1] == 1;} \\ A146085
isok(n) = !((n+2) % 3) && isa((n+2)/3); \\ Michel Marcus, Dec 09 2018

Extensions

More terms from Michel Marcus, Dec 09 2018

A147845 Odd positive integers a(n) such that for every odd integer m>=7 there exists a unique representation of the form m=a(p)+2a(q)+4a(r).

Original entry on oeis.org

1, 3, 17, 19, 129, 131, 145, 147, 1025, 1027, 1041, 1043, 1153, 1155, 1169, 1171, 8193, 8195, 8209, 8211, 8321, 8323, 8337, 8339, 9217, 9219, 9233, 9235, 9345, 9347, 9361, 9363, 65537, 65539, 65553, 65555
Offset: 1

Views

Author

Vladimir Shevelev, Nov 15 2008

Keywords

Comments

Since, e.g., 27=17+2*3+4*1 and 17=a(3),3=a(2),1=a(1), then 27 has "coordinates" (3,2,1). Thus we have a one-to-one map of odd integers >=7 to the positive lattice points in the three-dimensional space.

Crossrefs

A145812 A145818 A033045 A033052 [From Vladimir Shevelev, Nov 19 2008]

Formula

a(n)=2A033045(n-1)+1

A153401 a(n) is the least positive number such that in the representation of 2n+1, n>=4, as a sum of the form (2*A000695(k)+a(n))+2(2*A000695(l)+a(n)), both of numbers 2*A000695(k)+a(n) and 2*A000695(l)+a(n) are primes.

Original entry on oeis.org

1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, 7, 3, 9, 1, 1, 5, 3, 7, 9, 3, 7, 1, 1, 19, 3, 0, 5, 7, 3, 3, 5
Offset: 4

Views

Author

Vladimir Shevelev, Dec 25 2008

Keywords

Comments

For a given c>=3, every odd N>=3c is a unique sum of the form (2*A000695(k)+c) +2(2*A000695(l)+c).

Crossrefs

Cf. A046927, A103151, A000695, A145812, A147568.
Previous Showing 11-16 of 16 results.

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

Content is available under The OEIS End-User License Agreement.