A036381 - OEIS

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A036381

Number of connected numbers (A029827) in the interval [2^(n-1)+1, 2^n].

0, 0, 0, 1, 0, 5, 8, 21, 42, 89, 180, 361, 720, 1438, 2867, 5696, 11282, 22392, 44340, 87887, 174045, 344719, 682767, 1352375, 2678305, 5305631, 10510870, 20824910, 41264654, 81776998, 162083352, 321295873

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OFFSET

1,6

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

From the 64 numbers with ceiling(log_2(x)) = 7, the following 8 are composite connected numbers: 85, 95, 99, 111, 115, 117, 119, 123. Among the others 13 primes, 4 true prime powers and 39 split numbers can be found.

CROSSREFS

Cf. A029827, A029837, A036378-A036390.

Sequence in context: A105634 A294124 A120036 * A363224 A277369 A140419

Adjacent sequences: A036378 A036379 A036380 * A036382 A036383 A036384

KEYWORD

nonn,more

AUTHOR

Labos Elemer

EXTENSIONS

a(21)-a(32) from Sean A. Irvine, Oct 29 2020

STATUS

approved