A373400 - OEIS

A373400

Numbers k such that the k-th maximal run of composite numbers has length different from all prior maximal runs. Sorted positions of first appearances in A176246 (or A046933 shifted).

1, 3, 8, 23, 29, 33, 45, 98, 153, 188, 216, 262, 281, 366, 428, 589, 737, 1182, 1830, 1878, 2190, 2224, 3076, 3301, 3384, 3426, 3643, 3792, 4521, 4611, 7969, 8027, 8687, 12541, 14356, 14861, 15782, 17005, 19025, 23282, 30801, 31544, 33607, 34201, 34214, 38589

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OFFSET

1,2

COMMENTS

The unsorted version is A073051.

A run of a sequence (in this case A002808) is an interval of positions at which consecutive terms differ by one.

LINKS

Table of n, a(n) for n=1..46.

Gus Wiseman, Four statistics for runs and antiruns of prime, nonprime, squarefree, and nonsquarefree numbers

EXAMPLE

The maximal runs of composite numbers begin:

8 9 10

14 15 16

20 21 22

24 25 26 27 28

32 33 34 35 36

38 39 40

44 45 46

48 49 50 51 52

54 55 56 57 58

62 63 64 65 66

68 69 70

74 75 76 77 78

80 81 82

84 85 86 87 88

90 91 92 93 94 95 96

98 99 100

The a(n)-th rows are:

8 9 10

24 25 26 27 28

90 91 92 93 94 95 96

114 115 116 117 118 119 120 121 122 123 124 125 126

140 141 142 143 144 145 146 147 148

200 201 202 203 204 205 206 207 208 209 210

MATHEMATICA

t=Length/@Split[Select[Range[10000], CompositeQ], #1+1==#2&]//Most;

Select[Range[Length[t]], FreeQ[Take[t, #-1], t[[#]]]&]

CROSSREFS

The unsorted version is A073051, firsts of A176246.

For squarefree runs we have the triple (1,3,5), firsts of A120992.

For prime runs we have the triple (1,2,3), firsts of A175632.

For squarefree antiruns we have A373128, firsts of A373127.

For nonsquarefree runs we have A373199 (assuming sorted), firsts of A053797.

For prime antiruns we have A373402, unsorted A373401, firsts of A027833.

For composite runs we have the triple (1,2,7), firsts of A373403.

A000040 lists the primes, differences A001223.

A002808 lists the composite numbers, differences A073783.

A046933 counts composite numbers between primes.

A065855 counts composite numbers up to n.

Cf. A006512, A007674, A049093, A068781, A072284, A077641, A174965, A251092, A373198, A373408, A373411.

Sequence in context: A148773 A148774 A093537 * A180621 A073051 A183930

Adjacent sequences: A373397 A373398 A373399 * A373401 A373402 A373403

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jun 10 2024

STATUS

approved