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A239639 Lengths of runs of the initial digits of semiprimes in decimal representation, cf. A239634 2
1, 1, 1, 3, 4, 5, 2, 4, 3, 2, 4, 4, 28, 32, 32, 27, 33, 26, 30, 28, 29, 278, 264, 264, 260, 257, 245, 262, 252, 244, 2456, 2380, 2329, 2320, 2254, 2325, 2231, 2244, 2214, 21852, 21400, 20923, 20773, 20548, 20528, 20258, 20156, 20219, 197249, 193162, 190540, 188288, 187308, 185657, 184788, 183856, 183441 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

.   n | a(n) | runs in A001358 having a common initial digit

. ----+------+-------------------------------------------------------

.   1 |    1 | [4]

.   2 |    1 | [6]

.   3 |    1 | [9]

.   4 |    3 | [10, 14, 15]

.   5 |    4 | [21, 22, 25, 26]

.   6 |    5 | [33, 34, 35, 38, 39]

.   7 |    2 | [46, 49]

.   8 |    4 | [51, 55, 57, 58]

.   9 |    3 | [62, 65, 69]

.  10 |    2 | [74, 77]

.  11 |    4 | [82, 85, 86, 87]

.  12 |    4 | [91, 93, 94, 95]

.  13 |   28 | [106,111,115,118,119,121,122,123,129,133,134,141,

.     |      |  142,143,145,146,155,158,159,161,166,169,177,178,

.     |      |  183,185,187,194,201]

.  14 |   32 | [201,202,203,205,206,209,213,214,215,217,218,219,

.     |      |  221,226,235,237,247,249,253,254,259,262,265,267,

.     |      |  274,278,287,289,291,295,298,299]

.  15 |   32 | [301,302,303,305,309,314,319,321,323,326,327,329,

.     |      |  334,335,339,341,346,355,358,361,362,365,371,377,

.     |      |  381,382,386,391,393,394,395,398]

.  16 |   27 | [403,407,411,413,415,417,422,427,437,445,446,447,

.     |      |  451,453,454,458,466,469,471,473,478,481,482,485,

.     |      |  489,493,497].

PROG

(Haskell)

import Data.List (group)

a239639 n = a239639_list !! (n-1)

a239639_list = map length $ group a239634_list

CROSSREFS

Cf. A001358.

Sequence in context: A091828 A305972 A121845 * A099816 A237273 A272025

Adjacent sequences:  A239636 A239637 A239638 * A239640 A239641 A239642

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, Mar 23 2014

STATUS

approved

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Last modified August 17 22:59 EDT 2019. Contains 326059 sequences. (Running on oeis4.)