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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A378979 Square array A(n, k) = 2*A246278(n, k) - sigma(A246278(n, k)), read by falling antidiagonals. Deficiency applied to the prime shift array.

Original entry on oeis.org

1, 1, 2, 0, 5, 4, 1, 6, 19, 6, 2, 14, 22, 41, 10, -4, 10, 94, 58, 109, 12, 4, 12, 38, 286, 118, 155, 16, 1, 18, 102, 70, 1198, 190, 271, 18, -3, 41, 46, 394, 158, 2014, 286, 341, 22, -2, 26, 469, 94, 1284, 214, 4606, 394, 505, 28, 8, 22, 148, 2001, 178, 2452, 350, 6478, 614, 811, 30, -12, 22, 178, 630, 13177, 262, 4842, 502, 11614, 838, 929, 36
Offset: 1

Views

Author

Antti Karttunen, Dec 13 2024

Keywords

Comments

Each column is strictly increasing.
For all k >= 1, A(1+A378985(k), k) > 0, and it is the topmost positive number of the column k.

Examples

			The top left corner of the array:
k=  |  1    2    3     4    5     6    7      8     9    10   11     12
2k= |  2    4    6     8   10    12   14     16    18    20   22     24
----+-------------------------------------------------------------------
  1 |  1,   1,   0,    1,   2,   -4,   4,     1,   -3,   -2,   8,   -12,
  2 |  2,   5,   6,   14,  10,   12,  18,    41,   26,   22,  22,    30,
  3 |  4,  19,  22,   94,  38,  102,  46,   469,  148,  178,  62,   502,
  4 |  6,  41,  58,  286,  70,  394,  94,  2001,  630,  476, 106,  2746,
  5 | 10, 109, 118, 1198, 158, 1284, 178, 13177, 1522, 1720, 218, 14110,
  6 | 12, 155, 190, 2014, 214, 2452, 262, 26181, 3216, 2762, 334, 31858,
  7 | 16, 271, 286, 4606, 350, 4842, 446, 78301, 5416, 5926, 478, 82294,
		

Crossrefs

Cf. A006093 (column 1), A306190 (column 2), A378978 (row 1), A378985 (row index of the topmost positive term in column n).
Cf. also arrays A341605, A341606 and A341607.
Cf. also A324055.

Programs

  • PARI
    up_to = 78;
    A033879(n) = (n+n-sigma(n));
    A246278sq(row,col) = if(1==row,2*col, my(f = factor(2*col)); for(i=1, #f~, f[i,1] = prime(primepi(f[i,1])+(row-1))); factorback(f));
    A378979sq(row,col) = A033879(A246278sq(row,col));
    A378979list(up_to) = { my(v = vector(up_to), i=0); for(a=1,oo, for(col=1,a, i++; if(i > up_to, return(v)); v[i] = A378979sq(col,(a-(col-1))))); (v); };
    v378979 = A378979list(up_to);
    A378979(n) = v378979[n];

Formula

A(n, k) = A033879(A246278(n, k)) = 2*A246278(n, k) - A355927(n, k).
A(n, k) = A372563(n,k) - A372562(n, k).

A378986 a(n) = 2*phi(2*n) - 2*n, where phi is Euler totient function.

Original entry on oeis.org

0, 0, -2, 0, -2, -4, -2, 0, -6, -4, -2, -8, -2, -4, -14, 0, -2, -12, -2, -8, -18, -4, -2, -16, -10, -4, -18, -8, -2, -28, -2, 0, -26, -4, -22, -24, -2, -4, -30, -16, -2, -36, -2, -8, -42, -4, -2, -32, -14, -20, -38, -8, -2, -36, -30, -16, -42, -4, -2, -56, -2, -4, -54, 0, -34, -52, -2, -8, -50, -44, -2, -48, -2, -4
Offset: 1

Views

Author

Antti Karttunen, Dec 14 2024

Keywords

Crossrefs

Even bisection of A083254, and of A297114.
First row of A379011.
Cf. also A378987.

Programs

  • PARI
    A378986(n) = (2*eulerphi(2*n)-(2*n));

Formula

a(n) = 2*A000010(2*n) - 2*n.
a(n) = A083254(2*n) = A297114(2*n).
a(n) = -2*A176095(n).
a(n) = Sum_{d|2n} A008683(d)*A033879(2*n/d).
Showing 1-2 of 2 results.