A329877 Lexicographically earliest sequence of positive integers such that for n > 1, the concatenation of a(n), a(n-1), ..., a(1), in binary, is a prime number.
1, 1, 1, 2, 4, 3, 7, 10, 18, 1, 13, 5, 2, 42, 3, 3, 22, 18, 23, 15, 29, 33, 23, 17, 5, 33, 3, 134, 94, 84, 6, 57, 103, 13, 92, 63, 90, 60, 156, 39, 10, 108, 114, 65, 78, 67, 52, 57, 11, 21, 114, 79, 366, 128, 76, 22, 382, 36, 88, 34, 68, 110, 2, 72, 14, 28
Offset: 1
Examples
The first terms, alongside their binary representations and the corresponding concatenations, are: n a(n) bin(a(n)) bin(A329875(n)) -- ---- --------- ----------------------- 1 1 1 1 2 1 1 11 3 1 1 111 4 2 10 10111 5 4 100 10010111 6 3 11 1110010111 7 7 111 1111110010111 8 10 1010 10101111110010111 9 18 10010 1001010101111110010111 10 1 1 11001010101111110010111
Programs
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PARI
print1 (v=1); for (n=2, 69, s=(b=2)^#digits(v, b); for (k=1, oo, if (isprime(v+=s), print1 (", "k); break)))
Comments