55551

Appears in sequences

• Numbers having four 5's in base 10.at n=21A043512
• Near-repdigit semiprimes with 5 as repeated digit.at n=29A105986
• Semiprimes (A001358) whose digit reversal is a pentagonal number (A000326).at n=38A115708
• Primes in carryless arithmetic mod 10 in which all digits except the rightmost are zero or five.at n=28A169984
• a(n) = (5*10^n - 41)/9 for n > 0.at n=4A173804
• Semiprimes formed by concatenating n, n, and 1 for n = 1, 2, 3,....at n=23A210711
• For k in {2,3,...,9} define a sequence as follows: a(0)=0; for n>=0, a(n+1)=a(n)+1, unless a(n) ends in k, in which case a(n+1) is obtained by replacing the last digit of a(n) with the digit(s) of k^2. This is k(7).at n=37A237344
• Number of n-node rooted identity trees with thinning limbs and root outdegree (branching factor) 7.at n=10A245126
• a(0) = 0, a(n) = previous term + repunit of length of previous term for n > 0.at n=41A247107
• Expansion of x*(1 + 5*x + 40*x^2)/((1 - x^2)*(1 - 10*x^2)).at n=9A322927