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.

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A282151 Numbers n with k digits in base x (MSD(n)=d_k, LSD(n)=d_1) such that, chosen one of their digits in position d_k < j < d_1, is Sum_{i=j..k}{(i-j+1)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 10.

Original entry on oeis.org

11, 22, 33, 44, 55, 66, 77, 88, 99, 102, 110, 113, 124, 135, 146, 157, 168, 179, 201, 204, 215, 220, 226, 237, 248, 259, 306, 311, 317, 328, 330, 339, 402, 408, 419, 421, 440, 512, 531, 550, 603, 622, 641, 660, 713, 732, 751, 770, 804, 823, 842, 861, 880, 914, 933
Offset: 1

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Author

Paolo P. Lava, Feb 15 2017

Keywords

Comments

All the palindromic numbers in base 10 with an even number of digits belong to the sequence.
Here the fulcrum is between two digits while in the sequence from A282107 to A282115 is one of the digits.

Examples

			If we split 2039 in 203 and 9 we have 3*1 + 0*2 + 2*3 = 9 for the left side and 9*1 = 9 for the right one.
		

Crossrefs

Programs

  • Maple
    P:=proc(n,h) local a,j,k: a:=convert(n, base, h):
    for k from 1 to nops(a)-1 do
    if add(a[j]*(k-j+1),j=1..k)=add(a[j]*(j-k),j=k+1..nops(a))
    then RETURN(n); break: fi: od: end: seq(P(i,10),i=1..10^3);

A282149 Numbers n with k digits in base x (MSD(n)=d_k, LSD(n)=d_1) such that, chosen one of their digits in position d_k < j < d_1, is Sum_{i=j..k}{(i-j+1)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 8.

Original entry on oeis.org

9, 18, 27, 36, 45, 54, 63, 66, 72, 75, 84, 93, 102, 111, 129, 132, 141, 144, 150, 159, 198, 201, 207, 216, 258, 273, 288, 330, 345, 360, 387, 402, 417, 432, 459, 474, 489, 504, 513, 515, 524, 528, 533, 542, 551, 576, 581, 585, 590, 599, 600, 642, 647, 657, 672
Offset: 1

Views

Author

Paolo P. Lava, Feb 15 2017

Keywords

Comments

All the palindromic numbers in base 8 with an even number of digits belong to the sequence.
Here the fulcrum is between two digits while in the sequence from A282107 to A282115 is one of the digits.
The first number with this property in all the bases from 2 to 8 is
10296444436. - Giovanni Resta, Feb 16 2017

Examples

			672 in base 8 is 1240. If we split the number in 12 and 40 we have 2*1 + 1*2 = 4 for the left side and 4*1 + 0*2 = 4 for the right one.
		

Crossrefs

Programs

  • Maple
    P:=proc(n,h) local a,j,k: a:=convert(n, base, h):
    for k from 1 to nops(a)-1 do
    if add(a[j]*(k-j+1),j=1..k)=add(a[j]*(j-k),j=k+1..nops(a))
    then RETURN(n); break: fi: od: end: seq(P(i,8),i=1..10^3);
Showing 1-2 of 2 results.