A227936 Triangular numbers which become primes when their rightmost digit is removed.

21, 28, 36, 55, 78, 136, 171, 190, 231, 378, 435, 595, 1035, 1275, 1378, 2278, 2415, 2775, 4095, 5778, 5995, 7875, 8778, 10878, 11175, 11935, 14535, 14878, 21115, 26335, 27495, 31375, 31878, 36315, 37675, 42195, 47895, 52975, 55278, 60378, 66795, 68635, 75078

Offset

1,1

Links

K. D. Bajpai, Table of n, a(n) for n = 1..10000

Example

a(3)=36: T(8)=36. Removing the rightmost digit gives 3, which is prime.
a(9)=231: T(21)=231. Removing the rightmost digit gives 23, which is prime.

Maple

KD := proc(n) local a, b, d; a :=n/2*(n+1);  b:=floor(a/10); if isprime(b) then return (a) end if; end proc: seq(KD(n), n=1..10);

Crossrefs

Cf. A225873, A225885.

Sequence in context: A009727 A337702 A168105 * A048012 A254368 A276674

Adjacent sequences: A227933 A227934 A227935 * A227937 A227938 A227939

Keyword

nonn,base,less

Author

K. D. Bajpai, Oct 06 2013

Status

approved