121415

Appears in sequences

• Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) for n >= 3 with a(0) = a(1) = 0 and a(2) = 1.at n=22A000073
• a(n) = ceiling(n*phi^17), where phi is the golden ratio, A001622.at n=34A004972
• Consider the sequence of 4-tuples {0,a,b,c} (c>=a+b; a,b,c>0) which have the smallest integer 'c' required to reach {k,k,k,k} in n steps under map {r,s,t,u}->{|r-s|,|s-t|,|t-u|,|u-r|}. This sequence gives the second term 'a' of these quadruples.at n=35A034803
• a(n) = T(3n+1), where T(n) are tribonacci numbers A000073.at n=7A074581
• Sequences A001644 and A000073 interleaved.at n=21A075676
• Partition the concatenation 468910121415161820212224252627283032... of composite numbers into successive strings such that the n-th string is a multiple of prime(n) and > prime(n).at n=3A077305
• Bisection of tribonacci numbers.at n=11A099463
• Inverse Moebius transform of Fibonacci numbers 0, 1, 1, 2, 3, 5, 8, ...at n=26A108046
• a(n) is the sum of the (1,2)- and (1,3)-entries of the matrix P^n + T^n, where the 3 X 3 matrices P and T are defined by P = [0,1,0; 0,0,1; 1,0,0] and T = [0,1,0; 0,0,1; 1,1,1].at n=21A109523
• Expansion of -x^2*(x^9-x^8+2*x^7-x^6+x^5-2*x^4+x^2+1) / ((x^6-x^4+x^2+1) * (x^6+x^4+x^2-1)).at n=44A114952
• Tribonacci numbers A000073 which can be the hypotenuse of a Pythagorean triple.at n=7A130611
• Tribonacci sequences A000073 and A001590 interleaved.at n=40A213816
• a(n) = Fibonacci(n+2) + n - 2.at n=23A255875
• Satisfies the tribonacci recurrence: a(n) = a(n-1) + a(n-2) + a(n-3).at n=20A282718
• Numbers of the form t_n or t_n + t_{n+1} where {t_n} are the tribonacci numbers A000073.at n=38A308189
• Number of compositions (ordered partitions) of n into squarefree parts not greater than sqrt(n).at n=20A369220