12121212121
domain: N
Appears in sequences
- Two-bell analog of A028355.at n=15A028359
- Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 1,2.at n=10A037487
- Undulating palindromic primes of form ABABAB...BA with alternating prime and nonprime digits.at n=18A039944
- Strictly undulating primes (digits alternate and differ by 1).at n=15A059170
- Smoothly undulating palindromic primes of the form (12*10^n-21)/99.at n=1A092696
- 1 concatenated with n 21's.at n=5A137466
- a(n) is the smallest number not already present that permits the cyclic repetition of the path 1,2 of the digits in the sequence.at n=19A165300
- Primes in A028359.at n=2A168535
- a(n) is the smallest prime of more than n digits such that the number formed by first n digits is same as the number formed by last n digits.at n=8A228566
- Underline all even terms; concatenations of underlined terms and of non-underlined terms both equal the concatenation of the entire sequence. This is the lexicographically earliest such sequence without duplicate terms and with an even digit among the first two terms.at n=31A307312
- Smoothly undulating alternating primes.at n=32A343591