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A227936 Triangular numbers which become primes when their rightmost digit is removed. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 26 18:30 EDT 2021. Contains 348268 sequences. (Running on oeis4.)