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A122467 Write n-th semiprime in binary, sum as if decimal numbers. 2
100, 210, 1211, 2221, 3331, 4442, 14543, 24653, 35654, 46664, 146665, 246675, 346686, 446796, 546907, 648017, 758018, 868029, 978140, 1089141, 1200151, 1311261, 2311262, 3311363, 4312373, 5313474, 6323484, 7333585, 8343695 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Partial sum of A122466. Write n-th semiprime in binary, sum as if decimal numbers. Primes in this sequence begin a(4) = 2221, a(5) = 3331, a(7) = 14543 and a(34) = 13398139.

LINKS

Table of n, a(n) for n=1..29.

FORMULA

a(n) = SUM[i=1..n]A122466(i) = SUM[i=1..n]A007088(A001358(i)).

EXAMPLE

a(4) = 100 + 110 + 1001 + 1010 = 2221 because the first 4 semiprimes can be written in binary as 100_2 + 110_2 + 1001_2 + 1010_2.

a(34) = 100 + 110 + 1001 + 1010 + 1110 + 1111 + 10101 + 10110 + 11001 + 11010 + 100001 + 100010 + 100011 + 100110 + 100111 + 101110 + 110001 + 110011 + 110111 + 111001 + 111010 + 111110 + 1000001 + 1000101 + 1001010 + 1001101 + 1010010 + 1010101 + 1010110 + 1010111 + 1011011 + 1011101 + 1011110 + 1011111 = 13398139 is prime.

CROSSREFS

Cf. A000040, A001358, A007088, A004676, A122466.

Sequence in context: A235272 A249702 A188245 * A185792 A027604 A116145

Adjacent sequences: A122464 A122465 A122466 * A122468 A122469 A122470

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, Sep 09 2006

STATUS

approved

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Last modified December 4 23:46 EST 2022. Contains 358572 sequences. (Running on oeis4.)