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

Author

Jonathan Vos Post, Sep 09 2006

Keywords

• base
• easy
• nonn

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.

Examples

			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.

Formula

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