21222

Appears in sequences

• Numbers that are the sum of 7 positive 9th powers.at n=11A003396
• n written in fractional base 3/2.at n=23A024629
• Every prefix prime in base 9 (written in base 9).at n=39A024769
• Dirichlet convolution of Fibonacci numbers with Bell numbers.at n=9A034750
• k th digit of a(n) is the number of different digits within 3 of k (not including k).at n=12A039989
• k th digit of a(n) is the number of different digits within 4 of k (not including k).at n=12A039990
• Numbers having four 2's in base 10.at n=3A043500
• Numbers k such that k | sigma_9(k) - phi(k)^9.at n=29A055703
• a(n)=phi(n^2+1)/n if (n^2+1) is composite and phi(n^2+1)==0 (mod n).at n=34A067926
• Partition the concatenation 1234567...of natural numbers into successive strings which are multiples of 6, all different and > 6. (0 never taken as the most significant digit.)at n=7A077299
• Integers k such that 10^k+39 is a prime number.at n=15A135108
• Base 4 perfect digital invariants (written in base 10): numbers equal to the sum of the k-th powers of their base-4 digits, for some k.at n=35A162219
• a(n) is the smallest positive multiple of n whose decimal digits are all 0, 1 or 2.at n=26A181060
• Numbers for which the sum of reciprocals of square of digits is an integer.at n=7A182452
• Numbers 3*n + 2 written in base 3.at n=71A190642
• Put the natural numbers together without spaces and read them five at a time advancing one space each time.at n=31A193493
• Triangle read by rows in which row n lists the binary words of length n over the alphabet {1,2} with no initial repeats.at n=25A211029
• List of primitive words over the alphabet {1,2}.at n=44A213969
• a(n) is the least multiple of n which uses only digits 1 and 2. a(n) = -1 if no such multiple exists.at n=26A216478
• a(n) is the least multiple of n which uses only digits 1 and 2. a(n) = -1 if no such multiple exists.at n=53A216478