A122467 Write n-th semiprime in binary, sum as if decimal numbers.

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

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