20100

Appears in sequences

• a(n) is the concatenation of n and 5n.at n=19A019553
• Smallest triangular number containing exactly n 0's.at n=2A036517
• Numbers whose sum of digits is 3.at n=32A052217
• Sum of the first moments of all partitions of n with weight starting at 1.at n=18A066184
• Smallest triangular number which is a multiple (>1) of the n-th triangular number.at n=23A068084
• Smallest triangular number whose final digits are A068125(n).at n=45A068126
• Triangular numbers with sum of digits = 3.at n=6A068127
• First differences of (n+1)^5-n^5.at n=9A068236
• Triangular numbers of the form 10*k.at n=40A069498
• Largest n-digit triangular number with minimum digit sum.at n=4A069672
• Triangular numbers whose digit permutations yield at least two further triangular numbers.at n=15A069674
• Triangular numbers with internal digits also forming a triangular number.at n=32A069702
• Numbers k such that k+1, k^2+1 and k^4+1 are primes.at n=44A070325
• Triangular numbers which are 6-almost primes.at n=16A076580
• Triangular numbers whose internal digits form a triangular number. Or triangular number such that deleting the MSD and LSD leaves a triangular number.at n=46A077366
• Smaller of the two successive triangular numbers which differ in the use of only one digit.at n=35A077759
• Row sums of A094307.at n=9A094308
• a(1)=1; thereafter, a(n+1) = 20*n^3 + 10*n.at n=10A101098
• Triangular numbers that are sums of two consecutive primes.at n=24A111163
• Triangular numbers for which the number of divisors is also a triangular number.at n=17A116541