80200

Appears in sequences

• a(n) = n^2*(n^2 + 1)/2.at n=20A037270
• Triangular numbers with sum of digits = 10.at n=35A068129
• a(n) = smallest triangular number having no digit in common with the previous term, with a(1) = 1.at n=31A068818
• Smallest triangular number with value of the internal digits = n; or 0 if no such number exists.at n=20A069692
• Sum of next n numbers/n if n divides the sum else n times the sum of next n numbers.at n=19A094260
• n+phi(n)+phi(phi(n)) is a cube.at n=29A116042
• Triangular numbers with only even digits.at n=15A117978
• Triangular numbers composed of digits {0,2,8}.at n=3A119055
• a(n) = n*(n+1)*(9*n^2 - n - 5)/6.at n=15A172075
• Triangular numbers T from A000217 such that (4*T+1)/13 is prime.at n=23A208294
• Number of (w,x,y,z) with all terms in {0,...,n} and at least one of these conditions holds: w<R, x<R, y<R, z>R, where R=max{w,x,y,z}-min{w,x,y,z}.at n=16A212752
• Triangular numbers divisible by the square of the sum of their digits.at n=8A243008
• Numbers k such that the symmetric representation of sigma(k) has only two parts and they meet at the center of the Dyck path.at n=20A262259
• Number of n X 4 0..1 arrays with the number of 1's king-move adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero.at n=4A284109
• Number of n X 5 0..1 arrays with the number of 1's king-move adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero.at n=3A284110
• T(n,k) = Number of n X k 0..1 arrays with the number of 1's king-move adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero.at n=31A284113
• T(n,k) = Number of n X k 0..1 arrays with the number of 1's king-move adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero.at n=32A284113
• Numbers k such that (26*10^k + 61)/3 is prime.at n=26A288824
• Chessboard rectangles sequence (see Comments), also A037270 interleaved with A163102.at n=40A317714
• Triangular numbers that are sum of squares of two distinct triangular numbers.at n=23A346386