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.

A282115 Numbers m with k digits in base b (MSD(m)=d_k, LSD(m)=d_1) such that, for one of their digits in position d_k < j < d_1, Sum_{i=j+1..k} (i-j)*d_i = Sum_{i=1..j-1} (j-i)*d_i. Case b = 10.

Original entry on oeis.org

101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626
Offset: 1

Views

Author

Paolo P. Lava, Feb 06 2017

Keywords

Comments

All the numbers that are palindromic in base 10 and have an odd number of digits belong to this sequence.
Here the fulcrum is one of the digits while in the sequences from A282143 to A282151 it is between two digits.

Examples

			10467: if j = 2 (digit 6) we have 4*1 + 0*2 + 1*3 = 7 for the left side and 7*1 = 7 for the right side.
		

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),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);

A282112 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+1..k}{(i-j)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 7.

Original entry on oeis.org

50, 57, 64, 71, 78, 85, 92, 100, 107, 114, 121, 128, 135, 142, 150, 157, 164, 171, 178, 185, 192, 200, 207, 214, 221, 228, 235, 242, 250, 257, 264, 271, 278, 285, 292, 300, 307, 314, 321, 328, 335, 342, 345, 350, 352, 359, 366, 373, 380, 387, 395, 399, 402, 409
Offset: 1

Views

Author

Paolo P. Lava, Feb 06 2017

Keywords

Comments

All the palindromic numbers in base 7 with an odd number of digits belong to the sequence.
Here the fulcrum is one of the digits while in the sequence from A282143 to A282151 is between two digits.
Numbers with this property in all the bases from 2 to 7 are: 53060873, 55161152, 151009636, 343518281, 505587488, 513015908, ...- Giovanni Resta, Feb 13 2017

Examples

			409 in base 7 is 1123. If j = 2 (digit 2) we have 1*1 + 1*2 = 3 for the left side and 3*1 = 3 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),j=1..k)=add(a[j]*(j-k),j=k+1..nops(a)) then
    RETURN(n); break: fi: od: end: seq(P(i,7),i=1..10^3);

A282114 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+1..k}{(i-j)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 9.

Original entry on oeis.org

82, 91, 100, 109, 118, 127, 136, 145, 154, 164, 173, 182, 191, 200, 209, 218, 227, 236, 246, 255, 264, 273, 282, 291, 300, 309, 318, 328, 337, 346, 355, 364, 373, 382, 391, 400, 410, 419, 428, 437, 446, 455, 464, 473, 482, 492, 501, 510, 519, 528, 537, 546, 555
Offset: 1

Views

Author

Paolo P. Lava, Feb 06 2017

Keywords

Comments

All the palindromic numbers in base 9 with an odd number of digits belong to the sequence.
Here the fulcrum is one of the digits while in the sequence from A282143 to A282151 is between two digits.
Numbers with this property in all the bases from 2 to 9 are:
898958160865, 1518029154732,... - Giovanni Resta, Feb 13 2017

Examples

			3485 in base 9 is 4702. If j = 3 (digit 7) we have 4*1 = 4 for tyhe left side and 0*1 + 2*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),j=1..k)=add(a[j]*(j-k),j=k+1..nops(a)) then
    RETURN(n); break: fi: od: end: seq(P(i,9),i=1..10^3);
Showing 1-3 of 3 results.