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.

A304241 Indices where Mertens function A002321 reaches record amplitudes between zeros.

Original entry on oeis.org

1, 31, 114, 199, 443, 665, 1109, 1637, 2803, 7021, 8511, 9861, 19291, 24185, 31990, 42961, 48433, 59577, 96014, 141869, 230399, 300551, 355733, 603151, 926265, 1066854, 1793918, 3239797, 5343761, 6481601, 7109110, 10194458, 12874814, 30919091, 61913863
Offset: 1

Views

Author

M. F. Hasler, May 08 2018

Keywords

Comments

A subsequence of A051402 and A304239.
These are the indices where the Mertens function M = A002321 not only reaches a record value (in absolute value), but also its largest amplitude between subsequent zeros (as to avoid many "intermediate" records).

Crossrefs

Cf. A002321, A028442 (zeros of M), A051400, A051401, A051402 (where M, -M, |M| reaches k = 1, 2, 3, ...).

Programs

  • PARI
    L=M=0;for(n=1,oo,if(m=A002321(n),abs(m)>abs(M)&&[M,N]=[m,n],abs(M)>abs(L) && (L=M) && print1(N",");M=0))

Extensions

More terms from Bert Dobbelaere, Oct 30 2018

A304242 Increasingly larger (in absolute value) extrema of the Mertens function A002321 between subsequent zeros.

Original entry on oeis.org

1, -4, -6, -8, -9, -12, -15, -16, -25, -29, 35, -43, 51, -72, 73, -88, 96, -113, -132, -134, -154, 240, -258, -278, -368, 432, 550, -683, -847, 1060, -1078, 1240, -1447, -2573, 2845, -3448, -4610, -6226, 6695, -8565, 9132, 10246, -15335, -17334, 21777, -25071
Offset: 1

Views

Author

M. F. Hasler, May 08 2018

Keywords

Comments

Values of A002321 at the indices listed in A304241.
These are those records of the absolute value of A002321 which are the maxima or minima between subsequent zeros. Figuratively speaking, these are the increasingly larger heights of the mountains or depths of the valleys of the graph of A002321.

Crossrefs

Cf. A002321, A028442 (zeros of M), A051400, A051401, A051402 (where M, -M, |M| reaches k = 1, 2, 3, ...).

Programs

  • PARI
    L=M=0; for(n=1,oo, if(m=merten(n), abs(m)>abs(M) && [M,N]=[m,n], abs(M)>abs(L) && (L=M) && print1(L","); M=0))
    
  • PARI
    print1(j=1);for(i=1,#A051402-1,while( A028442[j] < A051402[i], j++); if( A028442[j-(j>1)]<=A051402[i] && A028442[j] < A051402[i+1], print1(","A002321(A051402[i])))) \\ Using precomputed vectors A002321 and A051402, e.g. from the b-files: {c=0;AX=apply(t->fromdigits(digits(t)[#Str(c++)+1..-1]),readvec("/tmp/bX.txt"))}

Formula

a(n) = A002321(A304241(n)).

Extensions

More terms from Bert Dobbelaere, Oct 30 2018

A304240 Extremum of the Mertens function A002321 between two successive (but not adjacent) zeros.

Original entry on oeis.org

1, -4, -3, -2, -4, 2, -6, 1, -2, 1, -1, -8, 5, -1, 1, -3, -8, 1, 3, -1, -1, -1, 1, -3, 2, -1, -1, -2, 2, -1, -1, -9, 1, 7, -5, -12, -1, -2, 1, -1, 3, 1, 3, -4, 1, -3, 2, 2, -1, -1, -1, -1, -1, 2, 1, -1, -1, 1, 1, 6, 1, 2, 1, -1, -15, -3, 1, -1, 2, 1, 2, -1, -1, 1, 1
Offset: 1

Views

Author

M. F. Hasler, May 08 2018

Keywords

Comments

In view of its definition, the Mertens function A002321 does not change sign between two successive zeros. Here we list the extrema, i.e., smallest or largest value, depending on the respective sign, between two zeros, excluding the case where these zeros are immediately adjacent, i.e., A002321(k) = A002321(k+1) = 0.
See A304239 and A304241 - A304242 for motivation & further information.

Examples

			The Mertens function M = A002321 is defined as partial sums of the Möbius function mu. At n = 1 it has the nonzero value M(1) = 1, and at n = 2 it has its first zero, M(2) = 0. Therefore we let a(1) = 1 by convention. (One can also consider that M(0) = 0, the empty sum, is an "initial zero" preceding M(1).)
Between the first and second zero of M = A002321, M(2) = 0 and M(39) = 0, M takes only negative values, and the largest in absolute value is a(2) = -4.
M(39) = 0 is immediately followed by another zero, M(40) = 0, the "empty" interval between these two is ignored by definition.
The next zero is at n = 58. Between n = 40 and n = 58 M takes only negative values, and the minimum is a(3) = -3.
		

Crossrefs

Cf. A002321, A028442 (zeros of M), A051400, A051401, A051402 (where M, -M, |M| reaches k = 1, 2, 3, ...).

Programs

  • PARI
    M=0; for(n=1, oo, if(m=A002321(n), abs(m)>abs(M) && M=m, M && M=print1(M", ")))

Formula

a(n) = A002321(A304239(n)).
Showing 1-3 of 3 results.