22155

Appears in sequences

• Doubly triangular numbers: a(n) = n*(n+1)*(n^2+n+2)/8.at n=20A002817
• The limiting sequence [A259095(r(r+1)/2-s,r), s=0,1,2,...,r-1] for very large r.at n=42A005576
• Numbers k that divide s(k), where s(1)=1, s(j)=21*s(j-1)+j.at n=39A014872
• Number of partitions of n into 10 unordered relatively prime parts.at n=42A023030
• Number of primitive (aperiodic) reversible string structures with n beads using a maximum of four different colors.at n=9A056333
• Triangular numbers whose index is a multiple of the sum of their digits.at n=37A067520
• Triangular numbers with sum of digits = 15.at n=29A068130
• Triangular numbers of the form 21*k.at n=40A069499
• Even order Taylor coefficients at x = 0 of exp( (sqrt(2)-sqrt(-2*x^2+2))/(-2*x^2+2)^(1/2) ), odd order coefficients being equal to zero.at n=3A081021
• Triangle, read by rows, where T(n,k) = C(n,k)*(C(n,k) + 1)/2, n>=k>=0.at n=59A107105
• Triangle, read by rows, where T(n,k) = C(n,k)*(C(n,k) + 1)/2, n>=k>=0.at n=61A107105
• a(n) = n*(n+1)*(n^2+n+1)/2.at n=14A110450
• Triangular numbers equal to the difference between a prime number and its index.at n=36A115887
• Triangular numbers for which the sum of the digits is a hexagonal number.at n=42A117309
• Triangular numbers n divisible by the number of triangular numbers smaller than n.at n=35A117519
• Numbers which are both lucky and triangular.at n=38A118565
• Triangular numbers composed of digits {1,2,5}.at n=9A119101
• Triangular numbers t which are average of two consecutive primes p and p+4.at n=24A129752
• a(n) = 3*n*(6*n + 1).at n=35A144314
• Number of composite numbers between exponents of successive Mersenne primes.at n=27A157894